I've made a somehow introductory post right here. I apologize for absolutely any kind of subjective way of talking, or accents on certain aspects due to my own opinion.
Sex magick can roughly be defined as any magickal act which uses sex as a component of the casting (as obvious as it is). Generally, sex magick is used in order to transcend, materialize, exhaust a desire, or get inspiration from it. It has always been part of of the magickal practice, though some see it as a lesser taboo, because, for some reason, it might conflict with their concept of what a mage is supposed to be and do. Stereotypically , it's seen that followers of the Left-Hand Path would dabble in it, thanks to its ability to express and control desire.
Useful Things to Know Edit
Sigilization - Sigilization [ Re1 ] is the practice of translating a desire in a certain sigil , activated by a state of gnosis. Knowing how to sigilize would surely come in handy in order to have an item to focus on (which will be activated by the purple/silver gnosis, as a combo) , or in order to help yourself get in the required state more easily. Sigilizing for your next ritual/magickal act to work would be one of those little tricks to boost an effect. A sigil can go as far as being a perfume or a pornographic image, but the goal in sex magick is to transcend lust to an ecstatic state which allows you to more easily manifest a certain effect [ Re2 ]. The irony is that you're basically transcending a desire in order to fulfill another.
Mantras - A mantra is a certain word, phrase, sound which has spiritual power. The mantra usually is believed to resonate with the particular energies you are evoking in the casting. Unfortunately , I am blind regarding the whole topic, so I can't offer any advice nor resource.
Gods - Evoking a god usually helps a spell with an effect under that particular god's domain. You might consider even implementing in your act the visualization of having sexual intercourse with that particular god or goddess. The fine tones of mythology might require you to start worshiping a god, or choosing carefully whom you wish to evoke, since evoking Pan would result in a different effect in comparison with evoking Eros. Invoking gods [ Re3 ] is the act of summoning them in yourself, assuming the archetypal aspects of the god/goddess which allows you to be more attuned to the particular spell you're doing, but can as well get as far as possession - which is an impressive experience, but we're talking about autoerotic congress, and supposedly there's no one around you to help you get out of the state.
Spirits - Evoking/invoking spirits is on absolutely the same level as with gods, the only difference being with the amount of external force you are dealing with. Using spirits you are already used working with would be advised. Spirits or servitors can be conjured as an effect of the magickal act - a common thing to summon would be an incubi or succubi.
Banishment - There was a time when I used to think that banishment [ Re4 ] is all about protection, and keeping spirits away or getting some sort of guidance from the elements while I cast my thing. What I didn't know is that a more important (in my opinion) relevance is that it gets you in and out of a magickal state of mind. Putting aside all the matters regarding 'casting a circle', or defining the micro and macro cosmos, a banishment ritual gets your mind focused on the right thing via rising an atmosphere, a certain feeling - in my case, the feeling that you're being watched and you have to play your role, do everything the right way. At the end, I personally prefer laughter as banishment , because of its deconceptualizative nature [ Re5 ].
Energy - Energy working is one of the most common things used in sex magick. Gathering and channeling sexual energy isn't the hardest thing to do - most probably you are already used with chakras, and you know how to use them. I personally don't work with them, but if it helps you wield sexual energy, that's great. Sexual energy builds up as the sexual act intensifies and is usually released once one reaches orgasms. Being able to ejaculate but not orgasm is a useful thing to know , as well as having some crystal or something of that sort in which you can store sexual energy.
Everything Else - Use your creativity, implement whatever you think it's useful.
Make sure you've got everything that you need. You've drawn your sigil, you've got all the candles, memorized your mantra, got an empty place in which you can't hear anything nor can you be interrupted. All in all, make sure you've got the place, you don't feel hungry (unless your goal is , first of all, to be in an exhausted state, case in which - congratulations, way to go!) , you're ready to do everything and you got all the mediums.
You normally would want to find the perfect position, contact the spirits you are working with to make sure they're going to assist you, draw the circles and everything's tidy. Start with the banishment ritual , invoke/evoke your spirits, gods, energies, whatever you're using.
The Act Itself Edit
You can start with visualizing a certain fantasy, or if you've evoked a god(dess), having sexual intercourse with them. This can get matters a bit harder since your goal is to transcend the desire. Use whatever toys, fetishes, techniques excite you, but keep in mind that your focus isn't the pleasure of your body, but release some demon, activate a sigil, or whatever your spell is supposed to do. If you have prepared a mantra , start chanting it since it will allow you to focus on your goal. If you have a sigil prepared, or an item you want to enchant, stare at it all the time. If you don't have any physical medium, you can just stare blankly or close your eyes ( be sure you aren't imagining anything apart from your goal, since you will fall in desire).
If you approach orgasm, stop what you are doing. Have a short, empty-minded pause, then continue. Repeatedly approaching orgasm [ Re6 ] but not releasing it builds more and more tension which , once liberated from it, allows you to cast a more powerful enchantment. Ignore all stimuli and reject any image your mind might come up with. Deny your desire of just releasing the sexual pleasure and work against it - this is the tension which allows liberation of desire and ultimately transcendence of it.
The Climax Edit
The climax point will fill like everything, from implosion to 'being one with everything'. It's consumption transferred all the build up force to the goal, the sigil, the evoked spirit etc. Your exhaustion though shouldn't slow you down, since the your intent might fade away without the proper maintained focus.
Now you should do your banishment, thank the spirits/gods, make sure the energy is sealed in the crystal, or basically clean up everything related to the act. If the enchantment of a sigil was your goal, then you should burn it, or get rid of it, since forgetting allows a better exhaustion/materialization of the desire.
That should be about it. Good luck with your spellcasting, or energy working, or sigilization, or whatever you sick minds can think of. Remember to endorse taboos, fight and play with obsessions, or whatever you fancy. Hope you enjoyed it. Most likely I will post some other guides in the future, on various topics.
Re1 - Fireclown's Sigilization Method
Re2 - The Book of Pleasure , by Austim Osman Spare
Re3 - Liber Null by Peter Carroll, Liber Lux, pag. 41
Re4 - Any kind of banishment ritual would do, from the Banishment of the Lesser Pentagram to the Lesser Ritual of the Hexagram ; I recommend reading Phil Hine's Introduction to Banishing Rituals
Re5 - Liber Null by Peter Carroll, Liber Nox, pag 83
Re6 - seriously, search about that - it's more useful than you might think
Hail Eris! All hail Discordia!