Orgasms. Why have one when you could have many? Am I right? Obviously I am.
Though a phrase like "multiple orgasms" may imply a focus on quantity and not quality, don't race to the first finish line in the orgasmic marathon you hope to compete in. Multiple orgasms will be easier to achieve via a buildup of sexual tension. I hate that I have to remind people to indulge in foreplay, but this, unfortunately, is the national sex-life deficit responsible for most orgasmic recessions and is, conversely, the key to your surplus.
Take the sexual path less traveled. Whether or not you're good at "mixing it up," we've all got our sexual patterns. When starting on your quest for multi-Os, instead of continuing on the classic line from a feel-up fest to digital/oral stimulation and then the inevitable penetration party, mix up your actions and types of stimulus and delay your first orgasm for as long as possible. Building up to and then backing down from your first orgasmic release will store up some sexual tension to donate to the multiple orgasms to come.
Your clitoris: learn how to use it and use it often.
That being said, take the pressure off yourself and your partners, both mentally and physically. If you go into a sexy scenario with a pre-determined orgasm quota, scorecards and those freaky little mini-golf pencils, you're likely to psych everyone out. For many people, even having the one orgasm can seem like a lot of work. Get there and enjoy yourselves and then assess the potential for more.
Physically, you need to literally take off the pressure. It's extremely rare that someone can just blitz through clitoral orgasms with absolutely no break in clitoral stimulation without twinging like they just bit down on a ball of tinfoil with a metal-filled tooth: not the path to another orgasm. While stimulation breaks can be 30 seconds for some and 10 minutes for others, take a moment to listen to your body and keep everything feeling good instead of overwhelming.
But don't be too underwhelming! Especially when "resting" between orgasms, it's crucial to learn to walk the sexual tightrope between over-stimulation and under-stimulation, each of which is a multiple-orgasm killer in its own right. While you don't want to punch it too hard, you also don't want to cool down too much. Taking a break doesn't mean getting up to get a snack or go outside for a smoke. Keep sexual energy up with other pleasurable play like neck-nibbling, body caressing and whatever else you freaks are into.
Remain open to different methods of stimulation, especially after having your first orgasm. Those who've been around the orgasmic block tend to have some old faithful tricks up their vaginas that'll always get them off, like periodically flexing their toes while applying pressure to the pubic bone and using well-lubed finger pads to apply quick, circular motions in the sensitive area a little upwards and to the right of the clitoris proper...or something like that.
In the case of multiple orgasms, go ahead and use your trusty tricks to get to your first kickoff orgasm in the series, but don't expect them to work their usual wonders for the orgasms that follow. A pressure princess may need you to lighten up, fingers just might not be able to reach the velocity of a vibrator, or maybe, just maybe, she'll be able to have an orgasm from penetration alone... gasp!
You knew the usual shout-outs to your PC muscles and partner communication were coming, right? JeJoue's Ami kegel balls are this moment's hottest exercisers for those sneaky muscles responsible for your orgasmic contractions, while simply voicing handy directional commands to your partner can be the strongest tool in your... box.
Finally, let go of what you think multiple orgasms are supposed to feel like. Some are 2 seconds apart, some are 20 minutes apart and some happen so close together that they might just feel like one never-ending XXX-plosion. My general rule when it comes to sex—if it's consensual and feels good, don't stop! And if you don't ever have multiple orgasms, who cares? At least you felt good trying.