Make sure your truck is rated to pull the trailer you intend to use. The vehicle should be in proper working order and well maintained.
Check overall condition of the trailer: tie downs, ramps, hitch, tires, etc. for proper operation.
Make sure the trailer coupler and towing coupler are the same size and proper capacity.
Trailer must be connected to tow vehicle before loading or unloading.
Lock tow vehicle brakes before loading and unloading trailer, and use chock blocks.
Place the load properly on the trailer, making sure the weight is properly distributed.
After connected to tow vehicle, make sure trailer is level, or slightly higher in front and adjust as needed.
Attach safety chains making sure you cross them.
Attach electrical plug and break-away switch (electric brakes), and make sure they are not dragging.
Make sure break-away battery is fully charged.
Check for proper tire pressure.
Check for proper torque on all wheel lug nuts.
Check all lighting on trailer and tow vehicle for proper operation. Plug brake controller into power outlet and adjust brake controller as necessary for proper braking.
Make sure trailer deck is clear of all debris before loading and before heading out onto the road.
Secure cargo or equipment to trailer on all four corners if possible and do not over-tighten binders.
Secure all loading ramps, and make sure jack stand is in up position.
Stow chock blocks.
After traveling a short distance, stop to make sure that the load is secure, and that all tie downs are tight.
Allow for greater braking distance when pulling a trailer, and generally travel at slower speeds.
Using this guide and taking the time to use precaution is the safest way to travel, but there is more to know. For proper tie down of a load and correct usage of a trailer, visit the Federal Motor Carrier Safety Administration website at www.fmcsa.dot.gov. There, look for Federal Regulations statues §392.9, §393.100 and §393.102. Also refer to your local and state laws regarding proper trailer use.