What should be done to tighten the steering on a 97 F-3507.3L?

There are several things that can cause this. First check your tie rod ends. Have a friend turn your steering wheel back and forth and watch each tie rod end closly for any slack and replace any that are worn. Next your steering gear box may have slack and can be adjusted. There is a nut on top of it with a bolt through the middle. To adjust it, loosen the nut about a turn and then hold it from turning. Then turn the bolt in the middle clockwise with a large flat blade screw driver. I would turn it about a half a turn to start with. Then retighten the nut letting the bolt in the middle turn with it. Also the shaft that connects the steering column to the steering gear box is notorious for getting slack in it on those trucks. Grab that shaft in the center between the firewall and gear box and check it for slack. Replace if necessary.