There are some simple rules. Don't be rude, and don't use hookup tricks or punchlines at the start. Better say hello, and be honest with your crush. You may say she is hot or just beautiful, or she forces your heart to beat faster. There are endless ways to start a conversation, and all situations are individual, so we can't recommend anything to you. Hmm… Wait. If you are on some sites, which provide you with premium emoticons, you can send them to show your status on those hookup sites. This will focus her attention on you, and your conversation will go much smoother.  Be clever, don't be moody, and don't be silly. That's all that we can advise you!