Buy Companies You Like
Legendary fund manager Peter Lynch (managed Fidelity Magellan Fund) says to look for companies you like to do business with. If you like to eat at Mcdonalds, buy Mcdonalds stock. If you like to buy furniture from R.C. Willey, buy R.C. Willey stock. This approach will help steer you clear of bad companies. However, if it was this easy and simple Peter Lynch wouldn't be a legendary fund manager. There are many more details to consider.
Pick the right sector
A sector is a portion of the economy. For example, energy, retail, and computers are sectors. Right now there is a lot of fallout in the financial sector due to subprime loans. There are many economic factors that can downgrade an entire sector. First, follow sectors to see what types of companies are doing well. Then, pick the #1 company in the sector. Pick the market leader.
In the last few years, the international sector has done extremely well due to the declining dollar value. The reason for this is because when you own a foreign investment, you're actually holding the stock in the foreign currency that was purchased with U.S. dollars. While the dollar drops in value relative to that currency, when you sell your investment it converts back to more U.S. dollars.
In any market sector, buy the #1 company
Most industries have 2-3 major players. It's actually amazing how universally true it is. The other fact is that the #1 company does far more business than #2 or #3. In addition, #3 usually gets a tiny trickle of business, in comparison. For example, market leader Dell Computers has a much better return than Gateway Computers. You will find this true for nearly all companies.
The fact is that the #1 company of a sector will outperform, on average, the other stocks by a mile. If you invest in any market leader, early on, you actually have a great chance to become a millionaire.
Avoid Small Cap Stocks
It is important to note smaller companies can give you much better returns than big companies. If you can successfully pick and time small companies, you will have the best returns of all. Many people try to pick obscure companies in hopes of gigantic returns. What you have to remember is that professionals that spend their whole life analyzing stocks can't pick these companies correctly. Statistically, you have less chance of success. This is why you can get a better return (more risk, more reward). If you think you can pick them, you are misleading yourself. You may want to consider a small cap mutual fund or emerging market fund instead.
Look At Management
Check to see if you like the management. Managers can make or break a company. Follow managers that care about return on equity. Some managers spend fortunes on frivolous items. Good managers make sure they can get the best rate of return on the equity they invest. If you follow managements spending, it will tell a lot about the company.
Margin Of Safety
The company must have enough cash reserves to cover a 20% loss (minimum). A lot of companies are in a position that everything must go almost perfect for them to make it.