Simple really say "you're in", then if someone catches you're eye send them the discreet and fully normal mating call of an owl "Twit Twit Twoo" and see what it leads to, can be via a message or a public call. What ever takes your fancy.
Rules are:
1) don't be a dick
2) respect filter
3) if someone isn't interested move on
4)it's a laugh
5) don't be a dick, just reminding you all of this one.