We just finished pointing out that it's difficult to see behind you when you're towing a trailer, but what about around you? How are you going to see other drivers who want to pass you or whom you want to pass? That's where having wide side mirrors that extend farther out from the vehicle than conventional mirrors do is handy. Often, these towing mirrors can be attached to conventional mirrors with clamps and extend the rear view. Some newer truck models, such as the Ford F-150, even have extendable side mirrors built in.
It's also important for other drivers to be aware of you and your trailer on the road. That's why the U.S. Department of Transportation requires that all trailers be equipped with lights that indicate when the tow vehicle and its trailer are about to turn or brake. The lights also should make the trailer visible at night. They can be hardwired into the trailer and connected to the tow vehicle through the wiring harness. Alternatively, wireless towing lights are available, too.
Now that you can see all around the trailer and everyone can spot you, you'll want to keep your eyes peeled for thieves bent on stealing your stuff.