Check out this amateur video!

Proper Racking Prevents Damage and Inconvenience - When fastening bikes to your car, truck or van, double check that all straps and fasteners are taut and remove any loose items such as bottles, pumps, computers or packs that could fly off when you start driving. For rear-mount car racks, run a strap through the spokes and around the bike frame to keep spinning wheels from rubbing on the paint or trim. And, make sure the wheels aren't too close to the exhaust because direct exhaust heat can actually melt/ruin bicycle tires. With both rear-mount and top-mount racks, know the clearances behind or above your vehicle to avoid hitting bikes on the road or against an overhang as you drive or park. And remember to lock your bikes together and to the rack itself to deter theft.