1. Get as much gas out as possible.
2. Disconnect fuel lines BEFORE lowering it.
3. Loosen all nuts before removing any of them.
4. Get floor jack in place and raise it to meet the gas skid.
5. Remove nuts slowly. Having a friend steady the tank will help.
6. Lower jack/tank and pull out from under vehicle.
Installation is reverse of above.
With the tank out, it is a perfect time to do any rear axle work (shocks, track bar, diff fluid, etc). LOTS of room to work that way.