Thats a pretty broad question. thier are several good medias and everybody has thier favorite. Try checking the media forum and the bargain basementfor discussions. As far as something to get you started, sony, verbatium or maxell usally uses good media. The most important thing to know is the brand doesn't matter. What maters is the media code which is the actual manufacture and model. Use this program to read the media code off of disks.
You will probably see more people talking about media codes than brands. When someone does bring up a brand, the first question is usally, whats the media code. Thier are several discussions in the forums about what brand media is what media code.
The most important thing is to find media that works well for you (using high quality media is the best way to start). two drives of the same make and model may not like the same blank disks (due to manufacturing variations I guess). Their is no one best disk but thier are several good quality disks, try some and see which work best for you. And of course discuss what media codes you are using and how they are working for you on the forums.