Use .mpeg files. The ideal DVD is a split of .mpeg video and separate .mp3 audio that is joined together in the final mix.
As far as programs, your OS should have something installed by default. Otherwise, go to a software review/download website (like
Free software downloads and software reviews - CNET Download.com) and search for something with good reviews. It's all about whether you're looking for an easy UI and efficient working, or if you want in-depth options. You'll find something for free, I'm sure.
As far as tips, just make sure you don't go over what the DVD can hold (I think standard DVDs hold 4.7 GB), and give it time to burn... it's usually a pretty slow process depending on what you're doing.