Keep in mind that you can put the landing gear down without unhitching the truck. Run it down just enough to start taking weight off of the rear suspension of the truck.
A couple of other thoughts:
If you have big or heavy (kitchen) slides, put the rear stabilizers down and snug them to avoid any chance of frame twist. Sure you can run them out without frame support. Dealers do it all the time. However once the frame is twisted even a little tweak, the slide will never close quite right again. Why take a chance. LG and Stabs take maybe five minutes. Time well spent.
Depending on your truck, you probably should unplug the umbilical. Some trucks cut power to the trailer when the key is off, but not all. It is a PITA to have to jump the truck off in the morning (particularly a diesel).
ON EDIT: If you are on asphalt put some kind of blocks under your jacks and/or stabilizer feet.