Call her out... every chance you get, accuse her of being a horrible sexual deviant. Accuse her of being a horrible sex machine. Tell her she couldn't find a man like you if her life depended on it... Place yourself on the pedestal, if she doesn't like it she has two avenues, either insult you, or tease you.
edit: Guess I forgot to include that you have to do this with a mocking tone. Nothing you say to anybody should be taken as being an insult. The only time insults should ever be used is to shock somebody's thoughts for a moment to get their mind off an illogical plane. Mocking tones are generally sarcastic in nature, or comedic.
Some call it c0cky and funny. That is generally what most LJBF or "Let's just be friends" type of relationships have in common, a lack of competition. When a female friend sees you as an equal on all fronts, she will call you a friend. She knows she can go to you with no fear of you making any type of advance, except for her betterment. There are cases where she will have an evil seed, and she will know that the only fear she has of you is one day, you may say no to doing her a favour of some sort. I hope you know which dynamic you fall under.
To keep an upbeat cometitive air about eachother, always make sure to make subtle accusations. Serious friends, friends who would take a bullet for one another, take jokes to extra levels. Places no other person would dare joke about... Why? It is because they know eachother's limits. In a budding relationship, you have to test these limits, because in the future, if your always playing it safe, your going to be in for a big surprise, that is if you can ever make it that far. So make sure, every time you have a gut feeling about what she is like, pause... than ask the question that is on your mind. Asking questions is good for some women, for others, they'll hate you for it. In the start, questions are "all right" after a time though, they EXPECT you to know a little bit about them. Enough to tease them about, enough to call them out on, enough to tell them when they know they are wrong.
I don't mean ALWAYS be accusing her. You can always have normal conversations about life, work, family, and friends. Just make sure that when you do have those conversations, remember the little things. Games she used to play, things she would NEVER do, things she would do ONLY when drunk, things she would do if caught up. Remember all the action possibilities that interest her. When you catch onto something that YOU actually know about, stop the conversation, and lead from there, lead her through the emotions you generally go through, since you've been through them all. You can have her lay down the basic storyline, and you fill in the desires and subtle action cues.
I think friends can develop into more. You just have to be around more, being more active, since you already have a different kind of relationship going on. Take every advantage you can get to make the relationship more sexually tensioned, create more chemistry. Heh, chemistry, start trying different combinations, the soultion with either blow up, fall flat with no change in properties, or a spectacular reaction will take place that is in your best interests. You know things about her, that no other guy does. That is why I said accuse her of things. As she is getting dressed in her room, DON'T be afraid of making a joke at her expense if you know she can take it, "you better not be wearing that blue tank top, you get rolls in your back when you do!!!"
Whoa, I almost forgot, accusations fall more in line with accusing her mentality, not her lifestyle or beliefs. You can accuse her of things that don't suit YOU. By YOU I mean, they don't suit your desires, your needs are not being met by her actions, so you are in all cases allowed to tell her what you want. She walks by you swaying her hips, or she bends over, she makes some food, she talks to another guy... tell her, that she, is teasing you. Tell her it's wrong for her to do those things, because your not allowed to touch. Tell her what you would do if you were another man. Tell her she better stop doing something, because your not going to be able to control yourself... If she continues doing what you asked her not to do, you can take "drastic measures"
It's better to regret taking action, than to waste your time wondering what could I have done better. Just take a chance, and hpe it turns out for the best, because she is only going to get more and more bored the longer she knows you want her, and the more you do nothing at all to make her want you back.
