This is part of a series of columns by retirement expert Dan Solin. Please bring him your questions in the comments box and he will answer as many as he can.

Is this a good time to invest, or should you sit on the sidelines until the market has "bottomed out"? This is the most common question I am asked.

It would be great if there was a way to tell when the market had reached its low. If you could do this, you would be able to buy stocks when the markets were taking off and retreat to risk-free investments, like cash and Treasury bills, in down markets.

Unfortunately, the data on timing the markets is very dismal.

One large study looked at more than 15,000 predictions by 237 market timing newsletters over a 12-year period. At the end of the period studied, 94.5% of the newsletters went bust. Not very impressive.

The financial media likes to hype stories suggesting that the markets are tanking or are poised for a rebound. These predictions are usually inaccurate and generally unreliable.

Here's a better question for you to consider: Should you be in the markets at all?

MarketWatch has an interesting article today about homebuilder and financial ETFs. The article, titled "Analysts say financial, builder ETFs signaling buy," interviews a couple of leading analysts who feel that both sectors have bottomed out and are "screaming buys."

Morningstar analyst Sonya Morris said that the Financial Select Sector SPDR (AMEX: XLF) is trading "at least 25% below what Morningstar thinks they are worth."

MarketWatch said in the same article, "Most of the analysts agree that valuations are attractive right now in the financial sector. They said that once the sector gets past the problems with the subprime crisis, probably by the end of this year, the shares could move fast."

I think these analysts are probably right, but that we're probably not through going down in the short term.

Zack Miller is the Managing Editor of IsraelNewsletter.com and a former equity analyst for a leading multinational hedge fund.

After rising more or less in line with overall market volume for years, there has been a noticeable surge since the spring in the relative turnover of selected exchange-traded funds (ETFs).

For the SPDR Trust Series 1 ETF (AMEX: SPY), which tracks the S&P 500 index, the average daily volume (ADV) compared to New York Stock Exchange Composite ADV increased from 6.1% in April to 16.8% last month. For the PowerShares QQQ ETF (NASDAQ: QQQQ), which emulates the Nasdaq-100 index, the numbers went from 6.3% to 14.1%. For the iShares Russell 2000 Index Fund ETF (AMEX: IWM), which mirrors the small cap benchmark, relative turnover rose from 3.4% to 6.7%.

Although it's not clear whether the activity was related to hedging or outright position-taking -- or both -- the sharp increase in activity suggests that there has been an important change in the underlying dynamic of the U.S. equity market. If so, it raises some interesting questions.

Could this be a sign, for example, that the influence of hedge funds, proprietary trading desks, and other speculative operators is expanding dramatically? Are investors of all stripes becoming increasingly focused on ETFs as an investing vehicle? Does this emphasis on trading bundles of shares mean that more individual issues are "mispriced"?

Whatever the case, this is a trend worth paying attention to.

Michael Panzner is a 25-year veteran of the global stock, bond, and currency markets and the author of Financial Armageddon: Protecting Your Future from Four Impending Catastrophes and The New Laws of the Stock Market Jungle.

The Wall Street Journal reports that PowerShares Capital Management LLC (subscription required) has "filed with the Securities and Exchange Commission for three new exchange-traded funds that will hold different combinations of other PowerShares stock and bond ETFs."

Here's why this is good for small investors: ETFs with their low expense ratios are a great product, and diversified portfolios of ETFs allow small investors to put together retirement portfolios easily, without the help of an expensive financial adviser.

But there's a problem: If you have a portfolio of $5,000 and divide it up among ten funds and have to pay a commission of $10 per trade, that works out to a front-load of 2% -- then another 2% when you sell. Unless you have a fairly sizable chunk of money to invest, buying multiple ETFs isn't very cost savvy.

Funds of ETFs will be a practical option for a lot of retail investors and could take market share from two groups that deserve to lose market share: financial advisers and big mutual fund companies.

This article is part of a 20 article special report on "Metals, miners and money".

The SPDR S&P Metals & Mining (AMEX: XME), "a play on hard assets, has delivered impressive gains of 52% over the past 12 months," notes Paul Tracy who has added the ETF to the Sector Trading Portfolio of The ETF Authority.

The advisor explains, "While investors shouldn't grow accustomed to red-hot annual gains of 50%, this ETF is an ideal way to gain exposure to this sector." Here is his review.

"XME has been in the right place at the right time. The ETF mirrors the S&P Metals & Mining and invests in hard assets like precious metals (gold), industrial metals (copper, aluminum), steel, and coal.

"According to studies conducted by research firm Ibbotson, this group has a very low correlation with other traditional asset classes, and a modest stake can boost long-term returns with negligible additional risk -- and that has certainly been the case lately.

A chart comparing the S&P 500 index to the MSCI EAFE index (a global benchmark comprised of stocks from Europe, Australia, and the Far East, which has an equivalent exchange-traded fund, or ETF (NYSE: EFA) ) points to a potentially significant shift in the relationship between U.S. and foreign equities.

That is, U.S. shares appear poised for a comeback, at least in relative terms.

Interestingly, this comes at a time when the world at large appears to be suffering from the consequences of a bursting U.S. housing bubble and a meltdown in the American subprime finance sector.

While it is too soon to say for sure, could this be a sign that U.S. investors are beginning to repatriate funds back home? Or that foreigners are reverting to past form with a knee-jerk move towards what has historically been seen as safer shores?

If so, foreign share markets may well suffer disproportionately in the wake of further unwelcome announcements and upheaval in global financial markets.

Some might say that's an ironic turn of events.

Michael Panzner is a 25-year veteran of the global stock, bond, and currency markets and the author of Financial Armageddon: Protecting Your Future from Four Impending Catastrophes and The New Laws of the Stock Market Jungle.

As exchange traded funds explode in popularity, investors are having a harder time finding bargains. According to Marketwatch, "In March, shares of closed-end funds covered by Lipper traded at a median discount of 2.34% to net asset value, the lowest level in 12 months. That level marked a 0.86 percentage-point decline from the end of February. During the one-year period ended March 31, the combined discount on closed-end funds declined by 4.29 percentage points."

However, the discount on exchange-traded bond funds has narrowed, meaning that many investors are looking for yield rather than capital appreciation right now. Investors should be careful about investing in ETFs for income, and evaluate them the same way you would evaluate a dividend-paying stock: Is the yield sustainable (What is the payout ratio? How will the payout be taxed?)

In many cases, I think some of the online high-yield savings accounts are the best bet for conservative income investing. They are safe, accessible, and provide yields of 5% and higher. Try ING Direct or Emigrant Direct.

For the past two decades, Jim Lowell developed an industry-leading expertise in analyzing mutual funds, with a particular focus on Fidelity funds. During that time he developed an annual feature known as his "Hot Hands" pick.

He explains, "Those who have followed my Fidelity Investor newsletter know that one trick in our proprietary playbook has been buying the previous year's best performing Fidelity fund and sticking with it for the new year. More often than not it turns out to be a big winner."

Given the growing popularity of exchange-traded funds, Lowell recently launched a new service, The Forbes ETF Advisor. And for the first time, he is applying his Hot Hands approach to ETFs.

He cautions that this strategy has not beaten the market every year. However, he says, "It has provided very healthy long-term result and I believe that many growth-oriented investors could improve their performance by putting a reasonable (5% to 10%) portion of their money to work following my Hot Hands strategy."

He explains, "Here are the ground rules for the strategy. First I looked at all of the diversified ETFs for each year between 2000 and 2006. I excluded single-sector ETFs, and on the international side, I excluded the geographically nondiversified (single country) international ETFs.

Please pardon me while I get a bit whimsical here. I get a prose bug from time to time. You must forgive me if this is light duty reading for such a well read crowd but I'm just having fun!
Submitted for the approval of our readers:

If I had bet upon the game and chance did let me win, let's say my take was twenty grand and now let us begin. I'd take ten grand right off the top and invest in GE (General Electric Company (NYSE:GE)). A stalwart and diverse keystone is paramount to me.

I'd next place 4k in the hands of Limited Brands (NYSE: LTD) for care. It's hard to take a loss, my friend, in sexy underwear. And candles bright and fragrances and things the ladies like, assure me that our LTD is on an upward hike.

Two grand I'd sure send Wal-Mart Stores, Inc.'s (NYSE:WMT) way, though kicked around a lot. I just can't seem to shake the truth they'd be a safer spot.

The Financial Times has a excellent series on Exchange-Traded Funds, an increasingly popular and often superior alternative to traditional mutual funds. In yesterday's article, the paper discussed active ETFs, which differ from the vast majority of ETFs in that they are not passively-managed mutual funds.

While the rise of actively-managed ETFs in inevitable, I think investors would do well to avoid them for the same reason that they should avoid traditional actively managed mutual funds: the expenses will be higher, the tax burden will be worse, and the fund managers will not do any better than the indexes, even before these expenses. The real strength of ETFs, in my opinion, is that they allow active investors to make macroeconomic bets. With traditional mutual funds, you can't trade during the day, and you may be charged a redemption fee if you hold the fund for less than a year.

I've been an ETF-evangelist on this site in several articles. But I was referring to passively-managed funds. If you decide to venture into the waters of actively-managed ETFs that's a whole other story.

I'm a little bit hesitant to write a review of Gerald Appel's latest book Opportunity Investing: How to profit when stocks advance, stocks decline...inflation runs rampant, prices fall, oil prices hit the roof...and every time in between. I consider myself a bottom-up fundamentals investor, and this essentially a book about investing based on macroeconomic trends with a lot of market timing information (but also some good background on economics). So I am probably not the target audience for this book.

That said, it's a pretty good guide to a style of investing that some will be more inclined to embrace than others. If you're a foreign policy junkie (you read The Economist, listen to All Things Considered, and enjoy the New York Times more than the Wall Street Journal), this is probably a book and a style of investing that will appeal to you.

The best thing about this book is that essentially presents a self-contained, one-volume source for a strategy of big picture investing. Chapters include "The Myth of Buy and Hold," "Putting Together a Winning Portfolio," "Income Investing," and sections about market timing (which is generally interspersed throughout the book), and exchange traded funds (for a terrific introduction to ETF's, check out Gerald Appel's son Martin Appel's book Investing with Exchange-Traded Funds Made Easy).

For a nice contrast, read this book along with the new edition of Burton Malkiel's A Random Walk Down Wall Street, as the books seem to contradict each other on nearly every single point. Appel believes that market timing and the study of charts and historical returns hold the key to the bright elusive butterfly of market-beating returns (also know as Alpha, in the parlance). Gerald Appel and Burton Malkiel are two of the most articulate spokesmen for these two radically different schools of thought. A televised debate would be one of the most fascinating television specials of the year (to me anyway...perhaps not so much for the Desperate Housewives crowd).