So the two of you are spending loads of time together, but how can you tell if your friendship is steady-or soon to be something more?
The thing about being friends with a woman first is that both of you have usually shared information about your past faults and relationships--information you probably wouldn't have shared if you both started out meeting in hopes of having a romantic relationship. If you want to start dating friends, there are some things you can do to let her understand that you are no longer interested only in friendship.
First, never express your feelings directly. Don't tell her that you see her as more than a friend. The way you make the change is by her confessing her feelings for you.
Don't be so readily available. Have enough going on in your life that no woman is a priority. Pursue your dreams, hobbies, etc., so your focus is mainly on yourself. Start noticing other attractive women when you are with her and commenting on it, but remind her that she is also very attractive. It's okay to compliment her like this while using your wandering eye. It also communicates that you find her attractive, but in a very detached way.
Talk about the things you require in a woman and give her conflicting messages that hint at your desire. This is a subtle way of qualifying her, developing relationship compatibility and will build her curiosity. Get her to talk about what makes a great boyfriend and what women want in a man. Listen to her and give her feedback. This will build her curiosity. Be comfortable letting her see your sexual side. After all she is your friend, but don't get hung up on topics like threesomes or you will seem like a pervert.
If you decide you really want to go the extra mile and start dating friends, do it step by step by slowly acting like a potential lover. Don't waste time chasing a woman that is not interested. The last thing you want to do is mess up a great friendship. It doesn't matter what exactly you will choose to do, you are always taking a chance that you will get rejected.
The longer she is thinking of you as a friend, you'll only have her in your dreams and continue to be stuck in the FRIENDZONE.