Has that best friend started to mean more to you than being simply a friend? Catch yourself fantasizing over the two of you being together? Typically, if a man makes a great best friend, they will also make a great boyfriend and lover. You already have a connection between the two of you, now you just need to find a way to change that platonic relationship into an intimate one. Now how are you going to get yourself out of that friend box and be seen in his eyes in a more passionate light?
The first steps need to be subtle and gradual. While you two have been friends, a comfort zone gets created in regards to conversation topics, and you become one of the guys. This is the image that you have got to change. It is time to make a little extra effort to become a bigger part of his life. Try to engage in conversation with things such as his plans, friends, family, and any other active element in his life. You want to become a cornerstone for him and expand the comfort to reach new areas.
While establishing these new areas you are also going to want to establish some new boundaries. You can still listen and be there for him on those sensitive topics such as girls and relationship, but this is your chance to show your desire to be a little more than just his friend. Tact goes a long way when handling this. You can show slight jealous or maybe add a little cynical humor in there which will grow and develop over time. Remember you aren't running a race and this change is gradual.
Next is the big step of changing that buddy image into you being a woman in which is attractive, connected to him, and more than one of the boys.