Preface: this will not work for everyone. i'm just sharing my experience.

I just got out of serious relationship 4 months ago, and I've been spinning plates ever since. I currently hold 4 FWB situations, and I also go on 2-4 dates/week. Sometimes these dates turn into FWBs, some are just 1NS/2NS, sometimes I never hear from the girl again, other times I think she completely sucks and I drop her immediately, and every once in a while, we become just friends. Just so you know, I would never take a girl out more than twice - like ever, FWB or otherwise. Anything past two dates gets interpreted as genuine romance.

The most important thing to remember when trying to create a FWB situation is: be upfront about your intentions and lifestyle. It's okay to be smart, cute, funny, and charming (she'll like all that), but don't let her think you're looking for your next girlfriend. Something simple like dropping a casual story about a date you went on three weeks ago (how great/terrible it was) can work wonders down the FWB road. 1) it a DHV, (other women approve you), and 2) you're not clingy or desperate for women's attention.

The second most important thing to do when trying to create a FWB situation is: deliver mind-blowing sex. I'm talking heart-pounding, legs-trembling, fantasy-level, god-like sex! Really get into it: tie her up, spank her (hard), go down on her for as long as it takes, force her hand/head to your cock, say her name, look at her with lust, make her desire you, talk as dirty as she'll let you, have her call you daddy, be the sex she wants to gossip to her girlfriends about the next day. The point is, no girl wants to be liable a whore for mediocre sex.

So, clear intentions/lifestyle and unworldly sex; done!

Then, right after you two finish up, while you're still drenched in sweat and her legs are still wet with cum, say: "we really need to do this more often." She'll smile and agree (of course she'll smile and agree, you just rocked her world), and then just explain your expectations. Personally, I go with: I want to be that guy you call when you need to get laid. After a long day at work, after a crazy Saturday night out, or when you're just really, really horny, I want you to call/text me, and I'll come over and fuck you.

It really not more complicated than that; the stage is now set. Most of the time, she'll coyly agree. And the next time she's down -assuming she was comfortable with the idea in the first place- either you'll get a call or she'll respond when you contact her.

I think women actually prefer the idea of FWB compared to a ONS. It a great way for her to rationalize that she's using you, as much as you're using her. Also, be sure to continue to deliver. Find out what she likes; find out what she hates. Become each other's sexperiments. Ask her, straight up, to tell you, show you, and teach you about sex. It builds intimacy and comfort. I cannot tell you how much I've learned about sex from women by just asking them to teach me.

Comments, discussion, and questions are appreciated.

Happy Hunting!

EDIT:

Foremost: none of this is meant to replace standard PUA techniques. You still have to develop attraction, push/pull, neg, tease, get her number, ask her out, kino, escalate, surpass LMR, etc. etc. etc.

Second: I find night-game tends to lead to more 1NS/2NS, not FWB situations. The attraction is too coated in alcohol/drugs/nightlife energy, and you'll both be completely different personalities sober. She ends up thinking you're just a player, and you do this every weekend.

Third:

be upfront about your intentions and lifestyle. It's okay to be smart, cute, funny, and charming (she'll like all that), but don't let her think you're looking for your next girlfriend.

I think this sentence is coming off a bit unclear. The most important takeaway from that is: you should express an attitude and lifestyle that matches your post date intentions. If you're looking for your next girlfriend, your conversations and emotions should reflect those intentions. If you're looking for casual fun, that needs to be obvious in the very nature of your personality.