How to put on camper

This is all good information,but to expand a bit there are a few things that you should be aware of. I was used to using the bed rail as one point to help guide me back parallel,then I got a newer truck. The newer trucks may be wider near the cab than in the back so you should check this out first,my bed rails are not parallel, that was the first problem that I encountered. It really doesn't make any difference as long as you are aware of it. The second thing that I noticed was that when I poured me driveway (which was before I got my first camper)I formed it to allow for water runoff so there is about a 2"-2.5" difference from left to right or passenger side to drivers side. This makes the greatest difference in loading the camper.I have loaded up 50 plus times and no matter what I do I cannot get it right. The front to back slope poses no problem. The problem is when the camper is is up and level the truck is not. I have thought of raising the camper up off level but I REALLY don't want to do that.I also thought of putting some wood under the wheels of the truck but I don't want to do that either. AS I said before not all trucks are the same nor are campers. I have a Bigfoot,and when loading everything is fine for the first 75% of the way. But the last 25% of the camper is wider and the back of the truck is narrower and the truck is at an angle making an already very tight fit tighter. I have worked out a system that works for me and I can explain it in another thread if anyone should be interested,my next camper landing spot WILL be level. My whole point is that there are a lot of variables involved and the more you know the better off you will be. I would like to note that I have used every method and advise,have the white line PERFECTLY painted in the back of the truck mat ( and check to make sure it IS centered before loading) and come to the realization that It IS THE DRIVEWAY. Knowing that I now have a system.

On edit if there are any suggestions I am sure they would benefit all.