Drive past the spot to be backed into with your vehicle and camper, slightly dipping into the space and out again as you pass. This small "scooping" will give your camper a better starting angle.
Pull your vehicle slightly away from the parking spot just before the rear of the camper reaches the spot. Strive to position the trailer so you can back as straight as possible into the spot with minimal turning.
Check the area behind the trailer for children, pets or obstructions. Ask a spotter to stand in front of the vehicle as you reverse to help guide you into the space. Open your windows and turn the radio off so you can hear the spotter clearly.
Place your hand at the bottom of the steering wheel -- not the top -- and slowly back your camper into its space, watching your spotter for assistance. By putting your hand at the bottom of the wheel, moving your hand left makes the trailer go left, and right goes right while backing up. It's simply more intuitive than having your hand on top.
Turn the steering wheel left and right from your bottom position to adjust your angle of approach, using slight movements and periodically watching your spotter to ensure a safe buffer. Avoid exaggerated turns, which can cause your trailer and vehicle to buckle or jackknife, necessitating another attempt.