Investors are facing a tough market these days, with the Nasdaq at its two-year low and the S&P 500 and Dow Industrials down for the year. Disappointing earnings news and concerns over a slowing economy have dampened market sentiment.

As always, Foolish investors should keep their heads in difficult times. Check out our collection of articles below to find ways you can strengthen your portfolio, learn how to uncover essential investing knowledge, and find out where to look for bargains.

Five Steps in a Weak Market

Sweating out the current decline in stock prices? Five steps should help you strengthen your long-term portfolio: Consider selling unprofitable companies that are weakening with the economy, eliminate margin, consider averaging into new or existing holdings, take stock of what you own and why, and consider shorting dogs!

Essential Investing Knowledge

Don't venture into this bear market unprepared. Investing in a company without carefully reading the financial statements is like climbing a mountain without any idea how to use a rope. You can borrow your buddy's rope, but you're relying on someone else's judgment and getting less than half the experience.

Valuation STILL Matters

Whitney Tilson tries to identify dominant businesses with strong franchises and wait until the price is just right. In this Fool on the Hill column, he discusses one company that recently met this criteria.

Seven Stocks Worth a Closer Look

Wondering if there are any bargains out there? Check out this recent Valentine's Day feature, which explores seven diverse investing ideas.

The Logic of Hoping for a Bear Market

As Bill Barker pointed out last year, if you are planning on saving and investing consistently for the next five years or more, a down market isn't always such a bad thing.