Hi there Cassie.Jill, what i commonly do is to follow the basic "buy low, sell high" but the problem is no one knows if that is the right level of low and the peak level of high.
During day trading I usually follow the Bollinger Bands and the Relative Strength Index. When the price go way below these two, that is the perfect time to buy.
Oppositely when the price goes way up beyond those two lines it is the time for me to sell. Most of the time it produces good revenue but not all the time.
It is good to have a couple of technique rather than relying on personal assumption alone.