is a good article on the Blue Ox web site for towing newbies. It talks about different methods of towing, and about different types of tow bars (car-mounted vs. motorhome-mounted), baseplates, accessories (auxiliary brakes, lighting), etc.
As Deerhunter says, selecting a toad is a personal choice. You first need to decide what type of vehicle you want and if you want to tow on a trailer, on a dolly, or 4-down. A list of vehicles that can be towed 4-down can be found on the "Motorhome Magazine
" web site. scroll down to Dinghy Towing Guides on the right and select the year vehicle you are interested in. Always, always, ALWAYS check the vehicle's owners manual to verify it can be towed 4-down without modification before buying. Do not rely on the salesman.
To tow 4-down, you will need a baseplate installed on the toad, a tow bar, a light kit (either auxiliary bulbs or a diode kit), safety cables and an electrical cable. An auxiliary brake is highly recommended and required in some states and Canadian provinces.