In general terms, time is on your side. Buying low is good, but unless you have a high risk tolerance maybe avoid stock categories which have a lot of potential unkowns or variables...they might take a long time to come back up, if ever. Examples: certain overseas stuff, certain tech stocks.

I don't have the time to do the research on individual stocks, so I just use mutual funds which have an operating philosophy in line with my investment preferences. This also dampens out the unexpected Enron-like situations.