Go over the trailer carefully checking all components are fitted correctly.
Fit the coupling and complete any wiring required for electric brakes. If a manual park brake is fitted, check the cables are secure and operating correctly.
If fitting hydraulic brakes, check all fittings are secure and the brakes have been bled correctly. Recheck fluid levels in the coupling reservoir.
Fit the winch securely to the winch post and fit the cable or webbing if not already installed. Check the winch roller is securely pinned.
Check that the tilt hinge bolts and nylock nuts are tight and secure. Check the tilt latches are working correctly and in place.
Double check your spring hanger bolts and "U" bolts on the axles that they are secure and tight and the wheels to the trailer.
Hand tighten the stud nuts to help align the rim on the hub and tighten the nuts in sequence. Ideally use a torque wrench to ensure that the nuts are tightened adequately.
Torque Settings for wheel nuts are
7/16" UNF 110Nm or 80 Ftlbs
1/2" UNF 125Nm or 90 Ftlbs
Fit amber reflectors along the side of the trailer, white reflectors on the front outside edge of the guards and red reflectors on the rear outside edge of the guards.
Put a dab of grease on the towball and hook the trailer up to your tow vehicle and double check that all the lights are working.
Check with your local licensing agency, transport agency or Department of motor vehicles on the correct method of ensuring your trailer is certified, registered and road legal. Fill in the appropriate forms and get the checks done as required. Once completed and road legal, you are ready to load up and hit the road!
For the first couple of outings with the trailer, take extra care to get used to the trailer and how it handles on the road. It may take a few minutes of driving for the brakes to bed correctly and if electric brakes are fitted - may need to be tweaked as components settle.
Every trailer trails differently and getting a feel for how the trailer handles takes time.
Good luck and happy trailering!