If you're towing a small trailer, then it will probably have a flat 4 wire connector. You can pick up a wiring harness for that pretty cheap. I got mine on
ebay (keep looking, the guy keeps popping up) for $30 plus $6 shipping. Drop shipped from the manufacturer, with full instructions.
Takes about 5 minutes to install, easy, 2 snap ins to connectors and one small bolt on the battery loosened and tightened.
One issue that I found was always having voltage to the 3 hot wires. This is normal, they're just not pumping any amperage. They work great on the trailer (Curt Manufacturing, guy in Atlanta selling them).
I pulled a 3,000 pound car on a 1,000 pound trailer to south Florida and back from Atlanta with no trouble whatever this last weekend.