Who’s that patent attorney you met at your last demo day? There was this guy who does 3 D printing… what was his name?
You know those business cards you accumulate at some entrepreneurial mixer? Where do those end up… in a stack on your desk or perhaps in file 13?
Find a cheap or free contact management system with tags and categories. Have the discipline to put these people into it; even though you think you may never call them.
Your network is a very valuable resource. Take care of it.