Think of adult dating sites as channels for social networks in that you need to connect, communicate and talk with those you are involved in to excel.
In reality, doing an online conversion is easier than trying to do it face-to-face in real life. Openers would be a fairly typical "Hey, what's up?" and before answering, you can take a moment to gather your thoughts. More specifically, in the warmth of your own house, you will communicate with other guys or girls. If one of them doesn't turn out as you planned, just focus your attention to the other entity and hope for a fast connection.
Get interested and start submitting invitations, reading profiles and talking with people. The more opportunities you get, the better the night's odds of scoring casual sex. Still remember to treat persons with dignity and the decency that they deserve. Nobody loves a mean person and you could even get thrown out of the forum for adult dating.