I seem to tie down a car a week to tow somewhere, untie, unload, repeat. This weeks tie down fun involves moving the Z back into my garage as well as the Lola which is currently tied down on one of our trailers.
I think all the ideas on this thread are good. If you do it a lot of towing and tying down though you won't wish to mess with the wheel straps as they take a good bit of time and while add safety, are not needed if you do a good job on your tie dows.
We use four straps, two in front and two in back, "Xed". Get some good quality straps, at a minimum
the type pictured or better. You'll be paying at least $25 for two straps, if not more. If you aren't you are probably getting too "cheap" of a strap. Had lots of those, lots of broken straps as a result. Those blue ones from Summit are good, had mine two years and work great.
On the RCR I put axle straps over each lower control arm, then attached the tie down to that. Cinch up tight, drive a few miles as others mentioned, check, then drive to the moon if you like. (the pictures of my Lola are on my buddies trailer and he's got bad straps don't use ones like that. One broke on that trip although no damage was done since we caught it quickly. I'm ordering him some real tie downs). One you get it right it won't move and getting it right just take a bit of doing til you figure out what is what. Now that I know my cars, got good bits I place it once, strap it down, and it never moves.
Whenever I get the cage stuff done I will have four tie down points put on the car too so that it'll just be a "clip and go" sort of affair with tying down. Might want to think about that if you plan to tow a lot.