I trained myself (and it wasn't too hard because I'm very suggestible, I guess) to level the pedals left foot forward. When we started riding a tandem my sweetie was comfortable only with right foot down, never leveled at all unless I announce it. (There are several reasons, one of which involves how we start and stop.) So I started doing that on the tandem. Now I screw up occasionally on both solo and tandem bikes occasionally, but generally it isn't hard to "do the right thing" when I think about it. The most likely screw-up happens when unexpected things come up on the road, bumps I didn't see in the shadows, cars entering suddenly, etc.