Have a professional program that runs alongside the basic program. When people apply, they have to offer something the place. Anything from a quiz, to a magazine, cooking, to lectures, to a strategy sharing night (where confidentiality agreements are signed and startups can reveal themselves to others). Maybe run a consulting company within the location. Make sure everyone has something to offer. Have some type of policy where new people and potential new people are shown in a public place. Also have some type of complaints box.