Not to be Mr. Negative or anything but you should really use the "Search" feature. This question has been asked at least a thousand times. But maybe you didn't know this already, seeing as how you said you're new.
But on a stock suspension, I've seen people cram as high as 33s with the proper fender trimming and bumpstopping. To be on the safer (and more economical) side, go with 235/75/15s, or 30x9.5/15r. I ran 30x9.5s without a lift and I had very little trimming to do. The good thing about 30x9.5s is that with a 3" lift they still look good and flex great!
1989 Jeep Cherokee:
Lift, tires, suspension, accessories, and other crap.