A short CHI paper from Lana Yarosh that sums up the basic 5 strategies that current health + wellness projects take, to encourage users behavior change.
Strategy Cheat Sheet
1. Set specific, short-term goals.
2. Set actionable goals.
3. Set goals the user is confident she can attain.
4. Use cues-to-action to trigger positive behaviors.
5. Allow users to increase their self-understanding through small-scale experiments.
All of the details + discussions of implementations at the link.