Your ability to handle and control your V tow vehicle and trailer is greatly improved when the cargo is properly loaded and distributed. Refer to your tow vehicle and trailer owner's manual to find out how to 

Balance weight from side to side

Distribute cargo weight evenly along the length of the trailer

Secure and brace all items to prevent them from moving during travel

Adjust the height of the tow vehicle/trailer interface

Apply load leveling (weight distributing hitch bars)

Most trailers and tow vehicles should be level (parallel to the ground) during travel. Check the instructions from your trailer manufacturer to make sure this is correct for your combination of vehicles.