There are a million little things you can do to prepare your female partner for cunnilingus. Not all women enjoy receiving oral sex, and it actually downright weirds some ladies out, but most at least wish to try it at some point or another. The techniques I will discuss here are valid for anything from a late-afternoon romp with the hotel maid before you go home from your vacation all the way up to a successful, healthy, happy marriage of 30 years or more. I won't be discussing the actual act of eating pussy, just how to prepare your woman (whether you're male or female).
The first order of business is, as many of the other writers here will tell you, to ask what your partner likes or doesn't like. If they have no experience, move on to step two, but if they have done this before, the odds are that they know what they like to at least some degree. When any partner says something is off limits, make absolutely sure you do not do it. This is not a negotiable point! The fastest way to kill a mood and perhaps a night is to do something out of bounds. On the other hand, if your partner makes a request, fit it in by all means. This is more important than it sounds; ignoring your partner's wants at any stage of the game wrecks trust between the lovers, makes one or both parties feel as though they're being used (not pleasantly), etc. Once you have established boundaries, noted requests, and so on, it's time to begin using your mouth.
From now on, every suggestion I make is just that- a suggestion. If your partner (henceforth referred to as "she/her") says something on this list is not good, it isn't good, don't do it. That said, let's begin with her mouth. Her mouth is one of the most amazing parts of a body that is built for giving and receiving pleasure of infinite different kinds. The female body is capable of performing in sports for your viewing pleasure, making dinner for your taste buds, conducting business and being a massive success, and any number of other activities. In terms of sex, her mouth can perform delicacies on you that never cease to amaze you. This should be a good hint to SPEND TIME WITH IT! Oral sex begins with the mouth... her mouth. This is your chance to introduce your lips to her, and allow her to see what they have to offer. Do not be afraid to kiss her, explore her lips, suck gently on her tongue, allow her to do the same. But when you are just beginning this journey, stick with the mouth. Resist the temptation to wander to her ears and neck for now. Yes, I know she tastes divine, but enjoy your first taste of the inside of her, and allow her to do the same. If you wish to be romantic, cup her head with your hands lightly (never forcefully do anything until you're actually eating her, unless she is good for spanking or other S&M type activities), whisper loving and/or sexy things to her. All part of your mouth.
Next is the neck and the ears. The neck has some very sensitive places on it. Think for a moment... the neck has loads of prominent veins, arteries, muscles, etc. It is a very vulnerable place on the body for this reason. Gently touch your own neck in several places and see what makes you shiver. Odds are, she will melt to you if you lick her and nibble on her in those places. I'm fond of wrapping my lips around a few specific places myself... one good one is directly below her ear, about halfway down her neck. The lower front is also good, and if you trace your tongue from about the halfway mark on her neck up to her chin, you're worked yourself back into a kiss. Regarding her ears, trace the outside of the ear from bottom to top or vice versa, and you should get a shiver. Suck on her earlobe, you should get a moan. Now here's what no man seems to be aware of: not every woman enjoys your tongue being shoved into her ear! I hear this complaint far too often. Be gentle! Ask first! Incidentally, these insanely sensitive places are all located very close to each other. Regardless of whether or not there's a God, goddess, higher power, or if it was all evolution and luck... that's intelligent design. Use it to your advantage and keep her guessing as to what place she's going to feel your lips next. Don't forget, your lips are magical, if used correctly. Be gentle, then be firm. Drag your lips across her neck as well as your tongue or your teeth. This works best if you have full lips, but can be done by smaller lips just fine.
Once you have finished teasing her from the neck up, it's time to begin your journey downward. Start with her collarbone. The space directly above it and below the neck is usually rather sensitive, and prone to your oral attack. The collarbone itself is also a nice touch, but using teeth is ill advised. There is only a tiny bit of skin between your teeth and the bone, so you'll want to be gentle here. Be very careful if you do use teeth, both for your teeth, and for her skin. The next obvious choice is her breasts. Good. Do not pounce on them, though, or you will have lost all the magic you've worked to create, both for yourself, and her. Kiss your way down to them. Avoid the nipples for a moment or two, licking the flesh instead. Don't forget, there is more to the breasts than nipples, and sometimes the rest of the breast needs some attention too. When you do arrive at the nipples, you can either tease them a bit with your tongue, or you can envelop them with your mouth and tongue. Do not use teeth for the latter, wait to bring in those guys until you've already got her moaning and shifting under your assault. Make sure to spend time on both breasts. If they're big enough, sucking on both nipples at once is sometimes fun, but you may want to check beforehand if both will reach your mouth at the same time.