Also, what kind of tractor and how big?
At the minimum, just removing both rear wheels:
(Please ensure the wheel bolts or nuts are loosened (just broken loose, not removed!) before you start jacking.) The tractor should be parked on a level concrete surface. Level is extremely important!
1) Two Jack Stands of sufficient capacity to support the weight of the tractor with the wheels on the axle.
2) Floor (preferably) or Bottle jack or sufficient capacity to lift the rear of the tractor and tire/wheel assemblies: I jack directly on the drawbar bracket and raise the wheels up so there is ¼ to ½ inch clearance (note, you may have to go a bit higher to accomodate the jack stands, then lower to the clearance above). Since I use a floor jack, I don't block the front wheels. As the floor jack raises, the tractor will move back slightly (jacks in an arc rather then straight up). You can block the front wheel if your floor jack has wheels or casters.
If you've got to use a bottle jack, make sure the pump handle is long enough that you won't be under the tractor. Other then the bottle jack lift straight up, the procedure is the same as the floor jack. BTW, I never get under the tractor. I use a length of wood (anything will work) to push the jack stands into position under the axle.
3) An assistant to help handle those big tire/wheel assemblies. This is especially important if the tires are filled!
That's enough to remove the rear wheels. If your tractor is larger, you may want to consider letting a dealer or professional tire shop handle this job.
I've only had to do this when I had my 670 (which had much smaller tires then the 790's). I followed exactly the procedure I just typed, including the assistant (a herniated disk and loaded tires are a bad mix). In this case, I had a leaking tire. The assistant also helped load the tire/wheel in to the pick up bed.
If I'm checking the inflation of the rear tires, I'll jack it (again, under the draw bar bracket) just enough so I can rotate the valve stem(s) to 12 O'Clock. I do not put the jack stands under the axle when checking inflation.
Be safe and good luck!