It is also a good idea to feel the wheel hubs to make sure that the bearings have not become excessively hot. Do so cautiously – they could be very hot and cause a burn. This could be a sign of potential failure due to improperly lubricated or worn bearings, or some problem with the brakes causing them to drag. Make sure to verify your brakes are working, any trailers that are 3,000 pounds or greater require brakes. Also, make sure that your tires are in good shape and there is no debris lodged in the tread of the tires which could later cause a flat.
Finally, a quick look at the welds in the tongue attachment area could prevent a serious problem. Finding a cracked spring or loose suspension nut before they become trouble may make your quick check time worth its while.