For starters, make sure you have properly functioning brakes on the trailer. Personally, I wouldn't have a trailer that only had brakes on one axle -- you wouldn't drive your truck with only brakes on one axle, why would you rely on only one pair of brakes to stop the weight of your rig AND the trailer? As far as I'm concerned the trailer should have enough brakes to stop itself and not need help from the tow rig to stop. Also, surge brakes are a bad idea as the only way that they work is by the trailer pushing the slowing tow rig to activate -- not much help if the tow rig can't stop.
X2 on the surge brakes. As they do not allow you to engage them separately. Which is very handy when your trailer starts wagging and pulling all over the place, or when its slippery, in these cases applyingthe trailer brakes only wil pull the whole rig straight, preventing jack knifing.
If in doubt, find a scale to weigh everything.
While this is not always an option when towing different things, you should deffinitely do it for your usual load, your offroad rig in this case. Scales are cheap, there is really no excuse for not doin this. Knowing what a given load weighs and feels like being towed, will give you a reference point to gauge what other loads may weigh or behave like.
Driving: Leave LOTS of room to stop, at least double what you normally would with your tow rig. Expect the dumbass with the little car to cut into the space you were trying to maintain in front of you. Make your turns WIDE, the trailer will "trail" to the inside of the turn and you don't want to hit anything.
IMHO this is the single most important piece of advice. Heed this warning.
Tongue weight: Make sure the tongue weight on the truck is right. Too much and you will have difficult steering. Too little and the trailer will push the truck around corners. If you have to, stop and adjust the vehicle on the trailer to balance the weight.
I believe 10 - 15% of the weight should be on the hitch, using a weight distribution setup will aloow higher %s. As a rule of thumb, if both tires on a tandem trailer are showing the same ammount of sidewall bulge, assuming similar tires, inflation pressure and alevel/even road surface, your load is well distributed.
In addition to what Jon mentioned, a trailer loaded to the rear too much will start wagging, and which is not desirable at all.
Thanks for starting this Thread Jon. :beer: