If you have a new habit that's not time-specific and doesn't take too long, try to do it first thing in the morning. It will not only get done (and be harder to forget), but the feeling of accomplishment can help your state of mind in achieving other tasks throughout the day. For me, lifting weights for the day takes 5 minutes to do a simple workout, but once it's done I feel like I've gotten something significant achieved and that makes me more motivated during the day.
Repositories are awesome, and we should have more of them.
I recently completed BJ Fogg's Tiny Habits, and it's a pretty lightweight way to install new habits (recommended). However, I realized I could use a better repository of useful habits.
So, please use this thread to suggest habits that you've found useful. Bonus points for evidence/anecdata of usefulness.
Obviously, 1 habit per comment makes upvotes a clearer signal of collective approval.