There are hitch mount racks and fold down. I am saving up for one right now.
For now, I just take the front wheel off and put one back seat down. I place the bike with the front forks facing the back of the xterra. There are two strap hooks or maybe they're for car seats or something, but they're in the floor and i use those to attach my strap...Then I just tighten it down across the top tube. I'll try to take a picture next time I go and upload it for you.
2001 Xterra SE 3.3L
Getting 19MPG right now. I'm proud of that, but want to get more out of it. I'm considering an HHO setup.