Most Helpful Guys
You're a chick so just saying HI to a guy would probably work. If you don't want to do that ask a question. Hey before we even start chatting, please tell me you like sushi? emoji. Something fun and light should do the trick.
If you meant literally -
And you gotta swipe right on the guy/press the heart button, and if they have done this too, you both match and then only you can message. But if either of you disliked each other you won't be able to.
If you meant it the other way -
Not really sure why you , being a girl, are asking this...
I mean do girls ever message first on there? I don't think so.
And more importantly you really don't have to, the guy will definitely message you. So maybe try to give him a chance and that's how you message?
Most Helpful Girls
You have to match with someone before you can message them. If you swipe right on him and instantly match, then you should be the one to message him. You can do that by simply saying "Hey there!" or by commenting on something on their profile/pics. There really is almost no wrong way... for women anyway.