The body shot has many variations, and there is no single "correct" way to perform (or enjoy) the act. Below are some suggestions:

The Three Holes
Have the body donor lie on a horizontal surface. Notice that three depressions (depends on body type and physical conditioning) around the neck-- the largest just below the larynx. Place some salt in the left, however much tequila fits in the middle (sometimes a shot, sometimes not; you probably aren't doing this strictly for accuracy of measure), and the slice of lime (you could substitutelemon) in the right. Lick the salt, inhale the tequila, and enjoy the lime at the finish. You get extra credit for performing this act sensually and for not making a mess (don't ask me how to collect that credit ;-).
The Tummy
Provided your partner has an flat abdomen, have them suck it in, and notice a convenient depression around their belly button. Fill with a shot of tequila. Depending on the situation, you may enjoy licking the salt from around their belly before doing the shot. Otherwise work something out. Anatomy permitting, it is sometimes fun to place the lime in the shot itself. Perform the classic salt, shot, lime maneuver.

Remember that there are many interesting ways to make this more or less interesting, and it is especially fun when done publicaly. Some consider it a violation of the spirit to introduce a glass, though it can allow other opportunities.