I would like to start by sucking up to you. You're totally awesome, and your column is hilarious, yet informative. Well done. (These compliments aren't lies; I just wanted to capture your attention.)
Now, enough with the sugar-coated crap. Here's my problem. Recently, my first (and currently only) boyfriend broke up with me. It's a long story, and I'd rather not go in depth with the details. However, there's one thing he asked me for: friendship. He has some things to sort out and could use me as a friend—and, quite honestly, I want to stay friends with him. I agreed to keep in touch with him, and this is great and all... but I don't know how to be "just friends" with my ex—let alone a guy in general. (None of my friends are guys, just so you know.) So, my question is, how do I be friends with someone I'm trying to get over my feelings for? Every time a guy has rejected me, I've never stayed close friends with them—even if they still wanted to be friends with me. I really want this to work out for the both of us, and that's why I need your expert advice on the situation.
I know I always say "I was once in your situation, Sparkler!" with a sage nod of my grizzled old head and a wizened puff of my old corncob pipe. And then I impart some passing wisdom, and disappear up the chimney, to deliver wisdom to other Sparklers. But honestly, I was in this exact situation, Sparkler! Naturally, I messed it up, but I think I at least started off well, and can advise you on that part. I can also advise you on how to have guy friends without accidentally seducing them with your feminine wiles, which are things that you have. I think they are located somewhere in the eyelashes area. Anyway, here are some DOs and DON'Ts for your situation.
DO be normalsauce.
Okay, this is the first and most important thing: have one interaction with this guy where you two hang out alone and it is absolutely completely normal. You may have to force the normalcy in there really hard. The first time I hung out with an ex who'd dumped me but who wanted to be friends, she seemed to be handling it quite well, and I seemed to not understand how to exist in society. She came to visit me, and was like "Hello! Whee! We are friends!" and I was like, "GREETINGS EARTH HUMAN, PLEASE EAT THIS PLATE OF NUTRIENTS," and then bumped into objects. I learned from this total failure and then scheduled another less-faily interaction, where we hung out together, and I resolved to be 100% not weird about anything. It worked surprisingly well. If you manage to hang out with this guy in an absolutely normal, relaxed context—even if you are relentlessly acting relaxed—the next time will be easier, and eventually there will be no weirdness left at all.
DON'T flirt accidentally.
This is pretty self-explanatory; just don't start telling lurid stories about showering or bras or whatever in front of this guy. Don't text him a :3 face at two in the morning. Don't pluck at his shirt, even if there is a giant caterpillar on there. Don't put your arm around him unless you are reaching across him to fondle a hotter boy. You get the idea.
DO be friendly.
You seem concerned about the fact that you don't have any friends who are guys, and therefore don't know what to do with one. Just treat him like a friend who happens to be a guy; that's all. Say friendly things to him, as you would to a person who is your friend. Don't put your mouth on his mouth, unless this is a thing you do with all your friends. Imagine that he's any old female friend of yours (except that she is super attractive to you in this scenario). Be normal to him; don't act different around him.
DON'T be too obsequious.
Don't make too many concessions in your attempt to remain friendly and keep this thing together. I think that if you're the dumped party, you're more likely to be all, "Ohhh I was a moron, I'm so sorry! Also I am fat and I suck and everything is my fault forever!" in the hopes that the other person will sigh and agree to take you back. This is terrible and you shouldn't do it. If this relationship is over, it's over; and even if it's not, debasing yourself is a terrible way to restart a relationship. Just... be normalsauce.
DO admit you don't know how to do this if things are going badly.
The worst-case scenario here is that I deeply confuse you, and you're so busy going "Am I too friendly? Oh wait did I just flirt accidentally? Should I anti-flirt??" and you create an awkwardness bubble around yourself that repels all human life and you and this dude never speak again. If the thing you want most out of this situation is that you and he remain friends, then you should make sure you tell him that. In my experience, exes who say they want to stay friends usually do mean it. If you simply explain to this guy that you don't know how to know a dude without knowing him, biblically, then maybe he'll try harder to meet you halfway, and won't misinterpret your uncertainty as anger or disinterest. I know my advice often ends with "Just tell the person the thing, with your mouth words," but it really applies this time; if he doesn't know what you want, and you don't know how to act around male friends, you two are very likely to blunder through this until you hate each other. As long you make it clear to him that you want this friendship to last, I think he'll do his part to make sure that happens.