Bear in mind that these are the parts of your body that not even your dear mother has touched since you were potty trained. And the biggest worry- what if your partner takes one look at your naked form and bursts into hysterical laughter? Oh, the horror. So, short of switching off the lights and insisting that your other half wears rubber gloves, what can be done? Apparently, it's all a matter of having confidence in your body. "I am attractive" you must mutter you yourself; as your cellulite tries to take over the world. Bullshit.
I say, focus on your partner's inner pain. He/she is also getting out his/her naughty girl/boy parts in front of someone. Your partner is also baring their soul (and their genitals) to be gawked at and possibly made a mockery of. This is the sex equivalent to imagining your scary audience naked- except in this case they actually are.
Now, you're naked. No clothes. Stop hyperventilating. Neither of you has fainted with shock, which means that you have the right number of fingers, toes, breasts, etc. Of course, now you have to actually do the deed. Sick bag anyone? Does the idea of actually doing it freak anyone else out to high Heaven?
I of course blame society. Children are bombarded with, "Jimmy, that's your pee-pee, don't wave it at the neighbours" and "Angels, don't show your panties, your granny doesn't appreciate it". Then suddenly- wham! Jimmy's pee-pee and Angela's panties are coming into contact for the first time and they both wish that they were having a nice game of scrabble.
I have no advice for this. None that wouldn't want to make you throw yourself off a cliff, anyway. My advice to myself however is this: Get over it, you bloody wimp. It'll be over soon and if it's crap you can always take up knitting. See? This is why you don't want my advice. On a happier note, sex is meant to be fun. Look upon it as you would a bouncy castle: your bits jiggle, you get out of breath and you look a bit silly. Sometimes you get bruises but all in all you have a great time (incidentally a friend of mine had to be rushed to hospital after a freak accident on a bouncy castle but this almost never happens).
I can only end by saying that I will continue to be paranoid until the day that I am actually forced (by peer pressure or drunkenness, most probably) to actually have sex. I'd like to say sorry in advance to who ever the poor sod is who's taking part in the vile act with me. If I say, "Is that it?" then I'm just joking. Honestly.