Making time to catch up with people at a conference
Skip the talks

Except for meals, most of the time at a conference is taken up by scheduled talks. Don't go to them. 

Ok, go to some of them. But if you want to get some work done, catch up with a colleague during a coffee break, take a look at the schedule, find a session (or two, or three) that seem extra boring, and agree to skip them. Use that time to go to a coffee shop, or sit in a quite space in the conference center.