If I had to pick two easily corrected issues I see show up time and again, I'd pick:

1. Optimizing the wrong thing.
2. Optimizing your process, when what you need is a different process.

Two questions I think help:

1. "What do you want to optimize?" (time? money? resource utilization? impact? innovation?)
2. "Is your ladder up against the right wall?" (equivalent to barking up the wrong tree)

A few well-timed and well placed questions go a long way.