Here's the thing about being an public person asking for crowdsourcing. It's all about social capital. In other words, you must first build faith that you are someone who can work and deliver. In my case, I designed small games and posted them for free on my blog. I made sure they're each uniquely branded with their own title, a bit of imagery and a compelling aesthetic. (In other words, I'm trying to be a John Harper of board games.) Here's how I pitched the first call for letters. Though that initial call was successful, I have since learned some better parameters to follow.
Prime the Pump: As you build a work history, others will be more likely to have faith enough to offer their own creativity to your project. Write about what work you've done so far, what challenges you face and why you need some help. So let's say you're ready to crowdsource something. First, outline very briefly what it is you want people to contribute and how you'll use their contribution. Post this on forums and on your blog.
Make It Easy, Specific and Fast: When you put out a call for crowdsourcing, set the parameters so each contribution is easy to submit. Allow people to enter their submission right on that forum thread or as a comment or on Twitter. In your call, be specific enough that people have a clear idea of what you need. For example, I recently called on my Twitter followers to come up with British-sounding names for Belle of the Ball. Lastly, make it fast by highlighting your favorite contributions in real-time. This last tip is why Twitter is such fertile ground for crowdsourcing. Just take a look at the next popular hashtag to see what I mean.
You Are A Curator of Solutions: I don't normally recommend crowdsourcing critical things like central mechanics for games. Still, I often spoke about my dilemmas with Do's early character creation process, for example. I eventually scrapped it altogether, despite many positive responses to it. I did this because chargen was too long and didn't let people actually play the game in the first session. Being open and specific about your direction lets others know their solutions were considered, even if they were not ultimately implemented. You'll get a million great solutions, but not all are great for your project.
Lastly, about "not too often." When you crowdsource, you're cashing in chips. You're trying to yield dividends based on your audience's interest in your project, your work history, and, yes, your popularity. When you crowdsource, know that you can't do it again for at least a couple weeks. Between now and then, work publicly, speak openly, offer help to others, respond to comments with civility (or not at all) and genuinely appreciate everyone's contributions.
» Photo: CC BY-NC-ND Matt Karp