• I always make sure the paper coffee cup’s seam (and sleeve fold if there is one) is directly below the sipping hole so I can drink it without looking. This produces a helpless feeling if the cup is made without a seam.
• I always wet my toothbrush before after applying toothpaste. Sometimes that makes the toothpaste fall off.
• When I was a kid, I kept track of how many clockwise and counter-clockwise rotations accumulated while moving around in a room, and always made sure to unwind them by spinning that number of times in the proper direction when leaving. Or, I tried NOT to accumulate any rotations.
• I can’t step on sidewalk cracks. If I do, I have to step on another one, with the opposite foot.
• When I didn’t have a rotary volume dial on my car radio, I always made sure to press the volume up and down buttons in multiples of five. Now I just make sure the digital marker is perfectly centered between digital ticks on the display.
• It bugs me if my Mac’s application windows aren’t all tiled or lined up, with no overlaps and no spaces (or a 1 pixel space, but it depends).
• I always use my turn signal, even when I’m pulling into a parking space or the driveway off our shared driveway. My reasoning is that if I neglect it even once, it could destroy my habit forever and I won’t be able to rely on it. Only slightly tongue-in-cheek.

I think there may be others that I’ve grown out of, or can’t think of right now. Outside observers may know of more.

Update: Today Jennifer caught me using my turn signal in the Wendy’s drive-thru. Yes, I was just following the the drive-thru around the building.