RCK

If the person buying your car is getting a loan, their loan officer will call your bank and get a payoff quote and send them the money directly with instructions to send them the title and lien release.

If they aren't getting a loan it's just a little more of a pain. The best way is to have them come with you to your bank with a cashiers check (cash works too, but not recomended), and they should be able to release the title right then and there for you.