Getting More Serious - Third Base
When you're fully comfortable with touching, kissing, and massaging each other on your top half, it might be time to turn your attention to the bottom half. Again, really make sure you're comfortable with each other in the previous areas! If you just leap to this area you'll be so nervous that you'll miss out on half of the sensations. You want to have taken your time to get to this stage, so the anticipation is really intense and you're both ready and eager for this part. There shouldn't be any hesitation at all that either of you want to do this, otherwise it makes the situation tense. Which isn't good.
Be Somewhere Quiet and Secluded
Yes, again. This is a REALLY big step for most couples and you don't want to be interrupted!! No siblings around, no friends to walk in. Make sure that you are definitely alone. Make sure you both ARE ready and sure about this, and wanting it. And make sure you built up to this through all the other stages so you're already comfortable with each other and with touching in general.
Wear Loose-Fitting Pants/Skirt
There will be enough nervousness about "what will it be like" and "am I big/small enough" without having to worry about the basic mechanics. Wear something that's easy to slip on and off. Go for zippers, not 80-thousand buttons. And make sure you WASH!! This area can be pretty odor-rich and you want the experience to be a positive, pleasant one. If you haven't shaved off your pubic hair, use conditioner in the shower! You can get hair burn from that hair just as you can from kissing a guy with a beard. NOT fun.
Hand Job - Masturbation
The first stage of any sexual encounter is 'sex' by means of the hand. This means that your hand fondles yourself or your partner to orgasm. Hopefully if you're already at this stage with another person, you've already figured out how to masturbate yourself to orgasm! That's the first step. If you don't know what pleases you, how is someone else supposed to figure this out! So the best first stage is to ask your partner to masturbate while you watch. Every single person masturbates differently. There's no "right" or "wrong" way to do it. And different people are pleased by different things - some like hard rhythms, some like soft gentle. Some like to be very wet, some like to be bone dry. So by watching your partner masturbate, you can learn these things. Pay close attention!
Once you've both done this, it's time to take over for each other. Now say that you want to try, and make sure you ask for suggestions. Ask if something feels good or if it should be done differently. Be sure to ask!! Again, it doesn't mean you're "bad" at it if you ask. Every single human being is different. So even if you did have many other people, you would still need to ask for this one particular person. This person is SPECIAL. Make him/her FEEL special and show that you care about what would please him/her in particular.
Oral Sex - Eating Someone Out
Now that you understand what this person likes with hand-sex, the next step is oral sex. Obviously you can watch hands but it's hard to watch when your head is actually down somewhere. So this has to come SECOND, after you already know what to do. Now try to recreate the same pattern with your mouth that you saw and did before with your hands.
If you're a guy, this will involve using your tongue to flick back and forth on her clitoris, and maybe to use your tongue to go in and out of her vagina. Note that EVERY GIRL IS DIFFERENT. Some girls really enjoy a tongue inside her. Some HATE it. Some like the tongue to be gentle, some like the tongue to be firm. Some girls like the tongue to go at a steady rate. Others like the tongue to keep speeding up. ASK her. She is SPECIAL and deserves to be pleased in the way her body responds to!
If you're a girl, doing oral sex on a guy involves sliding your wet mouth up and down on his penis, just as you did with your hands. You can use your hands too, putting them below your mouth and sliding your mouth and hands as a unit up and down. Since you've already learned what speed and rhythm and firmness to use from using your hands, now it will be even better - because it's the right technique, but with the gentleness of the tongue. Use your tongue to tickle the shaft as your mouth goes up and down. Spend some time just on the head, going up and down on it, before going back down the full length of the shaft.
If he's going to come and you don't want to swallow it, fine, grab a napkin. If you don't mind swallowing, then that's fine too. Either way, don't act as if it's "nasty". It's just a normal body fluid, like sweat. I would hope you get sweaty during lovemaking and don't mind that!