Here's another excellent cheap accessory ($3.99 at Auto Zone). It's a magnetic bracket that snaps around the wiring harness of the towing package wiring. There were already a couple of threads on this item, but I thought it would be a good addition to this thread as well.
The bracket consists of 2 plastic halves that unsnap and snap together. The photo on the far left shows the item packaging. This product is made by Hopkins Manufacturing Corporation (a.k.a. "Hoppy"). The phone number for sales is: 800-524-1458. The phone number for technical support is: 800-835-0129.
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www.trailerwiring.com)
The second photo from the left shows how you lay your wiring harness in the one half that is designed to accept it. Then you just snap the other half on. The magnet is plenty strong, and obviously there will be no problem finding steel to stick it to. Plenty of that available under our beefy trucks.