An audience (even if it's the family dog...but in that case, don't expect a laughing response)
Step1
Mentally prepare yourself. Know the joke like the back of your hand. There is nothing more embarassing for a joke teller than to fill in the joke with "uhm" and "uh" while scrambling to remember exactly how it goes.
Step2
Practice in the mirror. Doing so will help you to see how you deliver the joke, what facial expressions work to enhance the humor in it, and what pace to say certain lines. You are your first audience.
Step3
Practice the joke for the family dog. This second audience will allow you to focus your attention on them, not yourself since you have perfected your art form in the mirror already.
Step4
Third time's a charm, right? Wait for the right moment to tell the joke. Once you decide to do it, go for it! Don't hesistate; it could stop your momentum in its tracks. Delivery is key. Beginning is key to the key.
Step5
Give it your all. Once you're telling the joke, keep it up - don't stop midsentence (unless, of course, that's part of the joke). You've rehearsed, sweated for it, run to the top of the stairs and yelled "ADRIAN!" for this joke.
Step6
Finish the joke up with an amused look on your face. Even if no one laughed, at least someone's amused. :)
Tips & Warnings
Have confidence. Even if it's a bad joke, you had the guts to put it out there. Be proud!
Have a good sense of humor. Even if it didn't go well, there will always be another opportunity to tell the same joke...or another one if your original joke goes horribly wrong.
Be conscious of whom your audience consists of. Some people are offended quite easily, others not so much. Be mindful of all.