1. Don't preach to the choir.
If someone is doing something that you've asked them to do, then don't keep telling them about the benefits of what they're doing -- just let them do it!
2. If you don't understand what's going on, then your input probably is not meaningful.
Nothing kills productivity quite like an overactive manager standing over your shoulder asking every 15m "So...what are you doing?"
3. Listen to your employees.
You hired this person for their expertise. The best way for them to employ their expertise is by letting them do what they think is right. Telling them that their approach is too complicated and doesn't turn up results 100% of the time without rationale is equivalent to insisting that their experience is rubbish.
4. Don't patronize your employees.
Seriously -- telling someone about the life lessons they should be learning from a situation is just rude. The other person is a thinking, breathing human being who makes their own decisions on what to do in life. Making them waste breath being a yes man doesn't help anyone except for inflating your ego.
5. Be consistent.
If you complain about one employee taking an advanced solution to a problem, don't then praise another employee who takes that solution and comes up with an answer.
6. Don't tell people to "think outside the box".
This especially applies when the phrase has become a part of your box of manager skills. Practice what you preach.