depending on what model you have, its usually a lot of things. the late 90's stuff had a plastic "L" bushing thing at the bottom of the steering shaft that will take alot of the slop out of it. spindle bushings and center axle pivot will add some too. tie rods will get sloppy along with the holes they go in if they were run loose. $50 and about 4 hours labor usually gets them back to new condition. Searspartsdirect.com should have every thing you need. If you want to save a little money, get the part number from the parts lookup and get on google shopping. usually you can find the parts about 20% cheaper through somebody that sells through amazon.com or ebay..
I have seen spindle bushings get so bad they eat up the steel that holds the bushing and axle bushings wear out the hole in the axle and frame. if they get that bad, just weld in a washer that fits tight on the bushing. I have even run a small weld bead where the bushing fits and hammered it in. (but that is a short term fix, they will get sloppy after awhile)