On a related note: My car locks all of the doors when I lock the driver's side door using the key. I make a habit of doing this every time I exit the car, since I have owned it (~3 years).
I have only been locked out once; the one time I was locked out was because I didn't lock the car on the driver's side! (I left through the passenger side to avoid 5 seconds of rain. Bad tradeoff.)
Another car thing I do mostly for habitual reasons is turn on my lights anytime I'm in the car, even during the day; this makes me less likely to forget at night, and has the bonus of being very helpful in certain daylight lighting conditions.
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.