One of the hardest things i've learned (and still fight hard to get over) is the greed factor..
When you buy a stock, I think you should have an exit strategy in place... % gain, target price, etc...
Once it gets there...THE GREED FACTOR kicks in, and alot of people (Including myself more often than i'd like to admit to) get greedy, and convince themselves that its going higher. Thus usually selling with less of a profit than the "Original plan" would have gathered them.
This is the 1st step in succesfull trading, IMHO.
Start with a plan & stick with it...
That would be my NEWBIE advise based on experience.
Good luck with the board,
Dave