my a/c pully turns but the compressor doesn't i know i have to change the compressor and the reciever drier but what else do i have to do? my truck is a 96 with extended cab

 

Be sure the a/c clutch is working before you decide to replace a bunch of parts. The center section of the a/c clutch/pulley should be stationary when the a/c is not selected.
I would turn the center by hand to determine if it is functional at all. If it cannot turn, you likely have internal damage. If it turns smoothly and has some resistance, take a good look at the clutch, switches, relay(s), dash control and the brush feeding power to the backside of the pulley.
If the clutch is bad, it can be replaced w/o replacing the compressor, and, pretty sure, without evacuating the system.

 

What tomw said plus one detail that may not be obvious regarding the switches if you don't have the manual. One switch inhibits the compressor from coming on if the system pressure is low. The other switch removes power from the compressor clutch if pressure is high. This is done to protect the system, among other things. Your switches could be OK, but the A/C won't come on if your system is low on pressure (refrigerant) due to a leak. There are ports in the system where you can hook up a pressure gauge. I think the auto parts stores will loan these out (I haven't tried). Also, follow the wire from the switch to ground and make sure the ground is nice and clean. Don't just look at it, remove the ground wire bolt and clean up the terminal.

 

the center section does not turn

 

if you do have to change the compressor, and dryer, the system should be vacuumed with an a/c vac before its refilled with Freon, or the moisture in the system will cause ice crystals, and **** everything up.

 

If the center section doesn't turn you're best to figure that out first, as it's alot simpler than replacing the A/C system. Here's an example A/C clutch: A/C Clutch - 1996 Ford Ranger | O'Reilly Auto Parts

You can outright replace it, or test for the coil getting energized. When the A/C is turned on it should be energized, click, and the center should start spinning with the pulley.

As also suggested, if the system is low or high, it will overide the clutch engagement.

 

If the compressor wasn't grinding and making noise it may be OK. Check the system pressure, cause as others have said it ain't going to come on if the system is low on R134A. The clutch ain't hard or expensive to replace...Google is yur friend.