- Easy ways to change one's environment to change one's behaviour (block sites, automatically transfer x% of the salary to a savings account...). That's probably the lowest-hanging fruit in this field: easy to communicate, easy to implement, usually very effective, basically no side-effects and one does not need to make an effort to change his/her behaviour.
- Examples of rules that can be used to change one's behaviour and stick to it (allowance to eat meat only on Saturday), and tips on how to get back to the rule once broken.
- Effective ways to improve reading speed. And resources for slow readers (e.g. text-to-speech softwares in different languages, tips on how to retain information).
- Tips on how to find out one's strengths and weaknesses, and advise on what to improve when (when does it make more sense to improve a weakness and when a strength?). It is probably easy to generalise the tips so that one can help others identify their strengths and weaknesses.
It is important that the feel of the project is realistic. Popular (bullshit) self-help normally implies that one can do almost anything regardless of his situation. This is often net-negative as, for example, not acknowledging time constrains often leads to too much commitments and a dramatic decrease in outcome-quality.
Including well-researched but not yet well-known health tips (I'm thinking mostly but not exclusively about nutrition and mental well-being) could be a good asset, as medicine is often quite slow up-taking new research. However, it is tricky (where is it not well-known?) and delicate (can induce people not to seek professional help when needed, who can benefit of the tip? can it backfire?), so I don't think that one should start here.
Just some quick links just in case that helps you or someone else. I am not saying these questions have been answered sufficiently and with strong enough evidence base.