Beginning to Invest

[bighomage]

I'm 18 and I've just recently decided to put some money in the stock market. I have about 1000 dollars invested in Walmart and I'm looking to invest another 1000 in something else. I was thinking about Best Buy, but I think I might have missed the boat by about a week for some of the biggest gains. I think I might wait for price to come back down.
Anyway, as young as I am, should I be investing in proven companies like Walmart, or should I be gambling on some smaller technology stocks hoping for big time gains.

Also, if you haven't figured out already, I'm pretty much a novice at this. I've read a couple of basic books, but I still don't know what to look for in a winning stock. Any tips and/or books, sites, etc. that I could benefit from would be greatly appreciated. I'm basically just asking for some help to get me started in the right direction. Thanks.