Yes, it's great to meet people off-line too!
If you're using Meetups then one thing you can do is check the profiles of the people who say they are going to attend the meeting. That will give you a bit of background and also show you their faces.
When you get there, try not to waste too much time talking to people who can't do you any good. Sure, you should help newbies – and from a practical perspective this week's newbie could be next year's success story (though I'd say help newbies because you're a nice person) - but don't spend too much time on it.
If someone can't help you then move on. I don't know if you're comfortable with that, and I know for some people this will take a bit of practice – to have the confidence/balls to walk up to someone and just start chatting. In my experience, though, people in IM are very willing to network – because they want to make good contacts too!
I like to keep a note of who I've met and what we discussed, as well. Because my memory is not really great, like my partner's is LOL, and next time I meet them – which might be in six months – I've got a chance of remembering what we discussed if I have some notes to refer to on my way to the meeting.