Sexual Massage
Male
The basic principle of male genital massage is that you should slow down, stop, or change what you are doing just before ejaculation becomes inevitable. The best way to accomplish this is for the man to give a signal just before this point is reached. This repeated "peaking" process can sometimes help men learn to have multiple orgasms without ejaculating, and can also be practiced during solo masturbation. Ejaculation provides a considerable spark of pleasure, but can leave men too fatigued to enjoy the rest of the evening or do a good job massaging their partner; opposite-sex partners who like to finish male genital massage with ejaculation should have the woman receive her massage first.
It's also fun to encourage your partner with hot talk. Letting your partner know verbally and non-verbally that you're actively enjoying his pleasure can be a powerful aphrodisiac.
As an aside, it should be noted that a nice feature of male genital massage is that an erection is not required for it to feel good; some massage strokes actually feel BETTER when the penis is soft.
Male genital massage strokes
There are many different massage strokes that feel good on male genitals. Unless he indicates otherwise, it's usually safe to assume that firm and consistent stroking will feel best. One approach that some people favor is selecting two favorite strokes, and for a period of time alternating between them every once in a while.
Healing Stroke: With the penis resting on the belly, cup the balls with one hand. The heel of the palm of the other hand glides up and down the underside of the penis all the way to the tip.
Anvil Stroke: Bring one hand down, letting it stroke the penis from the top all the way to the bottom. When it hits the bottom, release it. Meanwhile bring your other hand to the top of the penis and repeat the stroke, creating an alternating motion.
Climbing the Mountain: Take the penis in one hand and gently, sensuously caress it for about ten seconds, then give it one quick up-and-down stroke. Repeat the sensuous caressing for about ten seconds , and then give the penis two quick up-and-down strokes. Repeat the caressing, then give three quick strokes, etc. Continue until ejaculation approaches inevitability.
It's up to the two of you whether to finish with an ejaculation. At the end of the massage, the sheet/blanket combination can be folded up over the person on the table to provide a warm cocoon. This can be a time of profound peace and contentment together.
Female
Female sexual response is often significantly different from male sexual response, in the following ways:
Female arousal tends to be more closely tied to emotional states, and feelings of warmth towards her partner.
Many women can come in two distinctly different ways: through G-Spot stimulation and through clitoral stimulation. Many women characterize the clitoral orgasms as "sharper" and the G-Spot orgasms as "deeper".
Women often vary considerably in what type of sexual stimulation they like, and how they like it done.
Arousal usually takes longer to build, but can often last longer and be more intense than that which men commonly experience, they can often have multiple orgasms.
Since women can sometimes enjoy stimulation all the way through one orgasm and into the next, there is little or no need for them to hold back in any way. Having orgasms in a series can cause arousal levels to float for a long time at a very high level.
Female stimulation
Women vary in their tastes concerning G-Spot and clitoral stimulation, so you need to be attentive and listen. A common preference is for their partners to begin with gentle rubbing over the entire vulva, to follow this with clitoral stimulation, and to finish with G-Spot stimulation or G-Spot AND clitoral stimulation. Please be aware that neither clitoral stimulation nor any sort of vaginal penetration usually feels good unless a woman is already in a fairly high state of arousal. When performing genital massage on women one often has a "free hand" which may be used to glide over the rest of her body, tease her nipples, massage her perineum, caress her face, form "connections" with other parts of her body (by stimulating some other part of her body at the same time as you are pleasuring her genitals), etc.
Although the genital massage styles presented below are some of the most commonly favored among women, there are many more.
Clitoral: When massaging her clitoris, learn what part of it feels best to her. Going in circles around it softly and rhythmically with a lubricated finger. Once you find something that feels great, consistency with it is often the key to further pleasure. Some women find that clitoral orgasms feel better if their vaginas are pleasantly filled: more fingers or an appropriately-sized dildo are good ways to accomplish this, though penetration of any kind usually doesn't feel good to someone who isn't aroused, so it probably isn't what she would want you to start right out with.
G-Spot: The G-Spot is an area on the forward wall of the vagina, just behind the pubic bone about two inches in. Pressing into it can be intensely pleasurable, but may cause a sensation of needing to urinate. Female ejaculation is sometimes a result of G-Spot stimulation. One easy way to stimulate the G-Spot is with your first and second fingers together. Make rhythmic gestures inside the vagina that look like the signal to "come here". Alternatively, one can rub the G-Spot in a circular fashion. Generally, it's the pads of your fingers which are pressing into her G-Spot. Another approach is to rotate your fingers inside her vaginal barrel with even pressure against all areas of it. Be aware that the shape of the vagina changes as a woman's arousal level increases. You'll probably notice the inner portion ballooning outwards during extreme arousal, which means that your fingers will need to rotate a little farther from center in order to maintain the same pressure on the vaginal walls. G-spot stimulation usually only feels good when the woman is aroused.
Vibrator: Vibrators generally work best on or near the clitoris. If the vibration is too intense, switch to a lower speed or put a cloth between the vibrator and her clitoris. It's OK to let your partner hold the vibrator. It's also fun for a vibrator to be used clitorally at the same time vaginal penetration is being performed.
Verbal and non-verbal encouragement: It's helpful to encourage your partner with hot talk Sexy complements, eye contact, etc. are also nice additions. Letting your receiving partner know verbally and non-verbally that you're actively enjoying giving her pleasure can be a powerful aphrodisiac for her.
Variations and Enhancements
Conscious breathing: Regular, conscious breathing is a powerful way to enhance both relaxation massage and erotic massage. If the receiving partner forgets to breathe, the massaging partner can remind him or her by breathing rhythmically and audibly. Some partners find that synchronizing the breathing between the two of them leads to wonderful sensations. Just don't hyperventilate...
Group massage gatherings: These can be put on with three or more participants. Participants divide up into groups of three or four, with one massage table per group. Each person in each group gets a certain amount of time on their table, and before massage begins this person tells the other people at his or her table what he or she would like, and what his or her limits are. This can be a lot of fun, and is a great way to practice asking for what you want sexually. It's good to start and end these by having everyone get in a circle, introduce themselves. Since you may end up giving three or four different people massages during an event like this, it's fairly common for the host and/or hostess to ask everyone to use gloves for all genital massage, and possibly for everyone to wash their hands before the next person gets on the table.
Finishing with Intercourse: Some partners like to finish with intercourse rather than the blanket-wrapping. Near the end of the massage one partner can climb on top the other and they can both fuck themselves to what are often very powerful orgasms. Thus, they can finish locked in each others' embrace.