As a viewer, nothing makes me want to interact more than a specific question. Like this! :P Polls are easy, and I'll fill them out about half the time. Like/favorites, less so. Direct questions that actually make me think my input will matter - that will hook me, if I've got time.

As a creator, I love it when people find bugs and give design input for my sites and projects, and they often have great ideas I don't think of. I probably like it best when I get someone asking for more of something creative I've done (asking to see more of a character or to see a finished version of a sketch), but who doesn't? I quite like audience cross-chat - it makes me feel like they are being entertained, even if I haven't got the time to be an immediate, active participant myself.