Just don't!
Why would you deliberately try to destroy a relationship?? There are plenty of fish in the sea.
Else wait for their break up.
Or IF YOU LOVE HIM TRULY, just go for it.. Dont let an anonymous answer stop you.. ;)
peace
If you're trying to get with a guy who has a girlfriend, what advice would you give?
Flirting is the main thing, just try not to do it so much when his girlfriend is around. I think guys secretly like it when multiple girls are after them, so don't be shy to make him understand what you're thinking, just be careful on how you act as other people will be VERY judgmental.
But yeah, just make yourself available, flirt and be sexier and more fun than his current gf and he should fall for you pretty easily lol
