Some of the most compelling new online destinations are driven by a participatory model that invites users to create, manipulate, share, curate and distribute digital content. This model creates opportunities for all sorts of network effects, allows for more compelling content to emerge from a diverse population, and engenders a more proprietary feel (a sense of ownership and responsibility), not to mention community involvement.

All very interesting, but how do designers plan for and build online destinations that succeed in this model? Well, there’s clearly no formulaic way to guarantee results, and it would seem that success depends on a lot of intangibles and unknowns like market vagaries, priming, timeliness, confluent fads, etc.

At the same time, we can see that sites that have developed robust and productive communities boil down to an essentially intrinsic value proposition. In other words, they don’t depend on community at the outset. Sites like flickr and del.icio.us make it possible to easily access your stuff anywhere there’s a web connection; the community stuff is great once you get involved, but there’s a sort of prima facie reason for using these sites that helps get you started.

That’s all really high-level, pretty obvious stuff, but here’s something more tangible—I’ve noticed a few best practices in terms of mechanics for enabling user-contributed content:

1. Got to start somewhere: make the button really easy to find
2. Bookmarklets + screen-scraping is the easiest way to let users to bring external web assets into the fold
3. In terms of user input (data, meta-data, etc.) make it clear what’s necessary and what’s optional
4. Leverage known data (time and place, any screen-scraped data, data derived from stuff the user just entered, data derived from stuff other people have entered for similar items, etc.) to enable “smart defaults” 
5. Use active assistance (e.g. field auto-completion) if possible
6. Allow users to preview their contribution
7. Keep things really simple and straight-forward. Framing things up in self-evident structures (1,2,3; what, where when, etc.) can help
8. Two options when users are finished: (1) take them back to where they started from or (2) take them to their newly uploaded content. Which alternative is best depends on the context, or you could give them the choice.

Any others?