The best thing to do is do like Matt said and read the old threads. Just dig in and browse around and you'll find tons of info. Other than that, scrap EVERYTHING containing metal. Collect, break down, sort, then sell. Talk to the scrap yard and find out their prices for different metals so you know what to look for and how to identify it.

If you're going for electronics mostly, computers will give you a far better return than stereos, VCRs, etc.