Sometimes, if you've recently met the person, it's just good to send a "nice to meet you" follow-up with no ask at all. You're very likely to get a response, and once the response has been made, you can make the simple ask (once they've responded once, they're probably more likely to respond again).

This is akin to the "one-line hook" in online dating: http://www.onlinedatingmatchmaker.com/match-messages/