What are some good guidelines to consider as to when to sell stock?

My financial advisor had me in several diversified and indexed funds. I did not think the market would hold ,which it did not--I sold them and moved them into a money market account before the bubble burst last year. Some of that money has been used to purchase stocks which have thus far resulted in a nice overall gain in my portfolio. I'm learning what to look for on the "buy" side but would like some advice as to what to consider on the "sell" side. These funds are invested in an IRA. If I had stayed where I was I would be looking at a loss greater than 10%. As it is now, I have a 5%+ increase since Nov of last year.