I recommend you stop by Little House Customs
and get some of the 'jack frame under here' stickers.
You look under the trailer, find the place where the frame is easiest to get at with a jack close to the wheel, and put the sticker on the camper body to indicate the location.
The goal of these little stickers is actually to tell tow truck operators, etc., where to jack the trailer so they don't damage the axle
or punch a hole in your floor, but it's frankly nice to carry your (scissor jack in my case) out to the trailer, slide it under at the sticker, peek to get the pad under the frame, then start cranking.