33's are fit in two common ways on TJ's:
1. 4" suspension lift, with 2" bumpstop extensions in front and 2-2.5" in the rear. Requires a SYE/CV shaft.
2. 2.5" suspension lift, with a 1.25" body lift, with 1-1.25" bumpstop extensions in front and 1.25-1.5" in the rear. The 1.25" BL usually accompanies a 1" Motor Mount Lift to offset some of the driveline angles.
Either way you go, figure on some or many of the following components: longer front brake lines, extended sway bar links front and rear, gears, brake and steering upgrades to accommodate larger tires, SYE, CV shaft, bumpstop extensions, new shocks, adjustable track bars, and a rear track bar bracket.
Here's how I put 33's on my LJ: Unlimited04's LJ Build - JeepForum.com