How can I approach my female friend to be my girlfriend?

There isn't some magical hurt free zone where you can't be hurt. You're going to have to take a risk. Ask yourself if you've been clear in your intentions. If you have, she is going to reject you. Deal with it. Tell her anyway. Then move on. If on the other hand, she doesn't know you like her, send out some feeler questions. What does she look for in a guy, crack jokes abouts sex and stuff. See how she reacts. Ask her on a romantic date. Crank up the flirting. See how she reacts. If she acts uncomfortable or whatever, just say what's up. If she responds positively though, go in for a kiss. You gotta risk it to get the biscuit. Good luck!

You will never know unless you ask. Maybe she has just been waiting this whole time for you to ask her. I would ask her to a dance if one was to come up. If not, ask her to something casual, like a concert.

There is a good quote out there that goes:
If you love someone, tell him or her. Forget about the rules or the fear of looking ridiculous. What is truly ridiculous is passing up on an opportunity to tell someone your heart is in vested in him or her."

Furthermore... you could think of it like this. What if she liked you but was too afraid to say something? What if she worked up enough courage to finally tell you how she really feels? What would you respond with even if you didn't feel the same? Would it really be that bad?

Go get 'er tiger.

girls love romance. do something really nice to tell her you love her.

I would make sure she likes you first just in case she says no. The only reason I say this is because 2 years of friendship might have given her the idea that if you were really interested, you would have asked her out already so she might not even be thinking of a relationship with you. Either way, I think it is best to admit your feelings for her. If you're straight with how you feel about her it will leave little room for her to jump around the subject and easier for you to get an answer. I hope things go well! Good luck.

Tell her. Say the words. It is better to know and be able to move on than to hover in uncertitude and anxiety. Take a slow, deep breath, hold it in for a few seconds, assert what you will say, and then say it.

Don't forget to exhale.