Well first as already said at least contribute the maximum you're company matches in your 401k. It's free money. I also recommend a Roth IRA. Deferred taxes FTW. As for play money. If you are a buy and hold type investor you can just start buying up stock. But IMO you might as well just invest the money in a stock based mutual fund.
For day trading you are going to need to start with a bit more money to make it work. Try to save up 8-10k before starting. You will also have to do quite a bit of homework and get to know the companies you want to invest in. This includes looking at the balance sheets, keeping up on the news, and listening to the quarter conference calls (or reading the transcripts). Day trading can easily be a full time job. You will also have to get to know the whole industry. How to pick out trend lines and stay ahead of the game. Which is all the stock market is, one big game.
Oh and try to keep emotion out of it. I've made thousands and lost thousands. When you let you're emotions get in the way, you make stupid decisions.
I try not to listen to tips. There's no harm in doing some research on a tip, but don't invest blindly or on just someones elses word.