After a few years on the TridionWorld forum, I've found the community participation follows from simple and meaningful gestures. We gravitate towards helpful responses and place trust in near strangers (some of whom would actually qualify as competitors).
We can encourage participation across Stack Exchange by sharing fascinating questions and answers with others in topics they might enjoy.
As an avid reader of leadership and communication books (Stephen Covey [7 habits], Alan Weiss, Daniel Pink [Drive], Scott Berkun, Seth Godin, and others), I've found "fascination triggers" to be a great lens to view technical community participation. Sally Hogshead describes 7 Fascination Triggers, though the three that apply are:
**IMO the most active Tridion community members (Tridionauts) are fascinated with (earned) prestige, trust, and possibly vice.*
For example, Stack Exchange appeals to:
- Prestige -- You might be fascinated with this trigger if you know who the top Tridion users are on StackOverflow. Do you appreciate a title? Are the badges appealing? Do you enjoy appreciation for a job well done?
- Vice -- sometimes it's fun to see and share how we've borked an installation. The war stories are frightful but sometimes hilarious. I see this in responses that start with, "why would you want to do X that way?" or end with "Dominic Cronin" (I tease, but I learned to ask better questions from you and Frank)
- Trust -- we have experienced and long-standing community members already on StackOverflow and other SE sites. We know who the top answerers are and conversely, you know who looks to your Tridion expertise.
Share unique, interesting, and amusing SE questions with colleagues, preferably in person. Let them know why it's important to you and make it specific to their expertise and readiness level. Sometimes a Tweet is enough, other times it helps to show someone in person. We'll each develop our own relationship and activity levels on SE sites--but I'm betting we get hooked along one of these triggers.
If all else fails, try beer... after hours of course. Harmonica playing optional.