Programming may be what draws people to technical conventions, but the most important interactions are the spontaneous ones that happen because you've got a lot of people with similar interests bumping into each other. The more of these an attendee experiences, the richer his or her experience will be.
The way to encourage these interactions is to create areas in the social space that people naturally gravitate to when they have nothing else to do. Here are two good techniques:
If possible, try to arrange the physical layout of your convention space so there's one traffic area that people more or less need to pass through in order to move between program items, the show floor, and their hotel rooms. Ideally this area should have places to sit and snack food nearby.
What you're trying to do is make a comfortable place to wait for events that tends to gather people and promote conversation.
The biggest single design mistake that people who run technical conventions make is failing to promote after-hours social interaction. If people just dissipate after dinnertime for lack of a place to find conversation, that's a sin and a waste. Any SF fan knows that the really worthwhile stuff at a convention happens between 9:00 PM and two or three in the morning.
The way to fix this is to have what SF fans call a `con suite' -- a suite or public room open at least from just before the end of daily programming until early the following morning. At some SF conventions the con suite never closes.
The con suite should feature lots of places to sit. It should have sodas and snack food, and perhaps beer. You'll need one or two people to run it, but this is light duty; it mainly consists of keeping the snack bowls filled and a bit of cleanup.
Informative signs are vastly more important than people usually realize. Your event won't work if the attendees and staff can't find things. It's also important to help attendees form a clear mental map of what's where which (among other things) tells them where the focal areas are.
Each program room should have a sign listing its event times. Key locations like the con suite, convention ops room, and green room should be signposted. The registration desk should have a large sign nearby featuring a floorplan of the public areas. Key intersections in the hall pattern should have this-way/that-way signs pointing to nearby locations.
Good signs reduce the hour-by-hour friction costs of running the event. This is so important that there should be one person on staff whose only pre-convention job is to worry about signage -- to walk through the space in advance locating and laying out signs, and then making sure they're printed and erected before the convention opens.