Before you start a business, you have to look at what the potential is, what your product or service is, and if there is a lot of opportunity to make a good deal of money over the long run. Or is it a "hit-and-run" product, where you're going to get in, make a lot of money, and then get out? That's not necessarily a bad thing; fads have made some entrepreneurs incredibly successful. But remember, once you're in business, one of the hardest things to do is to know when it's time to get out, to let go. And if you guess wrong, if you try to make a classic out of a fad, you are going to start losing all the money you have earned. And no one wants to do that.

Excerpted from Start Your Own Business: The Only Start-Up Guide You'll Ever Need