if a stock moves up 10-15% during the day, then its usually a good idea to take the profits. You also have to consider the overall market itself. Volume and market depth is really important IMO. Gives you a very good indicator on what is a good entry and exit point.
However the most important thing I've learnt in day trading is: 1: Don't get emotionally involved in the stock (not in a sexual way of course lol). I mean, get in and do what you have to do and get out.
2. Always have a game plan! How much are you prepared to risk losing. What return do you want from this trade?
