My Outback is 35 1/2 feet long and before I left the dealer parking lot I practiced turning and backing right there. My previous camper was 31 feet. You wouldn't think 5 extra feet would make all that much difference, but it did.
First thing I noticed, going forward, no matter how hard I tired, I could not jack-knife the tongue (going forward), turning either right or left. So immediately I knew I could turn my truck at the tightest circumference (going forward) and never have a problem.
Second, I watched my mirrors how the trailer tires tracked when turning a sharp as I could (going forward), and the tires really tracked shorter, which immediately I knew, if I ever got into a tight turn, I probably could not do it.
I then tossed a 2x4 I carry for leveling in the parking lot and attempted to turn a corner around it. I imagine the guys at the RV dealer ship probably thought I was looney or something, but these little exercised taught me a lot, immediately.
This was our 3rd trailer and I was surprised how much more distance it took to make a successful turn. But once I realized the distance (from the parking lot exercise), I knew the trailer's limitations, and I've never had problems since.
Sometimes, it means pulling out into the middle of an intersection before starting your turn. Sometimes it means taking the opposite direction lane to make the turn, like semi-trucks have to do sometimes.
Round-a-bouts are still my biggest pain in the neck! When Round-a-bouts have curbs on both sides, it's really scarry. I simply hug the truck to the outside of the circle and let the trailer track on the inside of the circle. Luckily, I've never been in one so tight the trailer tracked over the curb. I watch the trailer tires in the mirrors all the time. My mirrors are electric and I move them as I make every turn so I can see the trailer tires all the time. The second mirror is a convex mirror (curved) and it's always positioned out-ward so I can see the trailer tires at the sharpest turn I can make, (going forward) either right side or left.
My advise? Before leaving the dealership parking lot, spend the time practicing IN the parking lot before you even make it to the road. Most dealers will have no problem with you doing this. If you ask, one of the techs may even ride with you and give you tips and help. This way, you will know the limitations of your rig (tow vehicle and camper) combined. It it time well spend!