You don't. You go to the date (in a public place, set by the app) and if there's something fishy about them you can report them to the app (there's an explicit feedback request after each date).
Ooh, you lost $12! And your date did too, and probably the account as well. As for the risk of getting murdered, I think it's unavoidable in any app (and in life in general) but probably worse if you organise the date by yourself.
