Disclaimer: I am no more qualified to give advice than Doctor Phil is to give weight-loss tips, Kimora Lee is to doling out fashion direction, or anyone at Cosmo is to providing tips to pleasing a man. But they do it. Granted, they have lawyers and shit-piles of money. But I don't. So remember, that anything you read here might be horribly, horribly wrong. Or it may be horribly, horribly right. My guess is as good as yours, just better.
Dear Add Vice -
I have a super-hot Italian fuck buddy that I've been kicking it to for about a year now. We totally click sexually. Whenever we hook up, we have amazing intergalactic sex that only gets better each time. We also have great rapport which makes me wonder, dear advice columnist, should I take this to the next level? If so, any advice on how to make him my boyfriend instead of just fuck buddy?
-BFNYC
Oh, BFNYC, why would you want to ruin a perfectly good relationship? With a fuck buddy (FB) you have someone that comes to your door with only one thing on their mind. With an FB you have someone that doesn't need to tell you about what happened at work that day or that upsetting dialog they had with their friend. With an FB you don't have to feign an interest in their collection of Maria Callas records/Spider-Man comics/Hummel figurines.
Before trying to flip you FB into a BF, first look at your own motivations. You have "amazing intergalactic sex" and a "great rapport", but this isn't enough. You're seeking more, but why? Are you seeing other people in addition to FB? If you're not, then you're being lazy. It's easy to stop dating when you have a convenient fall-back plan. Are you thinking about him when you do have sex with other guys? If so, don't confuse these thoughts of fantasy with thoughts of romance. You're not missing him; you're fantasizing. Sometimes I think about Manuel Torres, but it doesn't mean I'm in love with him.
Next look at his motivations. Assuming you know more about him than just that spot on his frenulum that makes him freaky, go through the same retinue of questions you would with someone you've just met. Is he closeted? Does he already have a boyfriend? For what other possible reasons has he not tried to advance the relationship?
Then consider the time you spend together in your "great rapport". If the basis of that rapport is only sex-based, that is possible to have with many. Even if it is based on subjects as the general workings of the world or how crazy other people are, you don't have something unique. What is needed is a commonality or at least tangential harmony of interests, tastes, and world-view.
With all of the above mitigating factors out of the way, you can pursue flipping your FB to a BF, and it's probably easier than you suspect. First of all, never make the approach to broaden your horizons before the sex. Right now the basis of your time together is the sex, and you don't want to mess with that. Put out, then pursue
During the post-coital period, make small talk inquiring what your FB will be doing later/tomorrow/on the weekend. If one of the activities matches one of your own interests, casually mention that fact. ("Oh, you're working on your bonsai? Did I ever mention that I minored in botany at university?") Do not offer to join them in whatever activity they mention. The next time they visit, again put out and then pursue. Follow up the previous conversation to display your maintained interest. ("How's your shimpaku doing? Are you keeping it in direct sunlight?") On your next meeting, again get your sex on. Then have a mutually interesting activity in mind, but don't mention it immediately after the sex. As he's getting dressed and ready to leave, bring it up, almost as an afterthought. ("Oh, you know what, I just read about The Steinhardt Conservatory at the Brooklyn Botanical Garden. Can you believe there's a museum just for bonsai? I want to check it out sometime.")
Boom. You're dating. From there you can see if fuck buddy works as boyfriend material. You had asked about turning your FB into an BF. And the correct short-form answer is that you cannot. But you can turn him from a fuck buddy into a date. If it grows from there, awesome. If not, keep having the great sex, but also keep dating other people.