What should you do if your best friend is going out with this girl you like?
it may suck, but you have to get over it (or at least pretend to... if you try any sabotaging make sure no one can tell)
You choose a girl you like who your best friend hates over your best friend and then that girl dumps you how do i get my best friend back?
if they where hot then hell yes! If you were going steady with this girl, a best friend would not interfere. However, you must also understand that is this girl does not feel the same way about you, you should not interfere with others approaching her, even a best friend. That would not be fair to your friend. I know it hurts, but it will pass.
What do you do if your guy best friend is going out with your girl best friend but he just told you that he had a crush on you and you still like him and hes aways flirting with you and ur flirting to?
I don't think that you should. My friend is going through the same problem. If you ask your best friend out, then it would be very awkward when you two break up. I would suggest that you try and find another girl that you like and get to know her. And, if you did ask her out, you wouldn't want to break her heart when you two break up.