The Twelve Commandments of Software Consulting

1. The client is paying you, not the other way around.  That means you are temporarily their employee: you answer to them.
2. You are a consultant, not a dial-up coder from a a body shop. You are supposed to provide advice, solicited or not - so do it.
3. Be respectful to your clients. Assume that they may have people on staff who are as talented, but they may be unavailable. Hence you being requested.
4. Don't talk down to non-technical clients, and don't use intimidating and baffling technical language. They want a business problem solved, not a lecture from Richard Feynman.
5. Help your client team: other external consultants, and all internal people. They also want to solve the problem.
6. You are a consultant: so consult. If a meeting is going south, speak up, and say your piece. It's why you are there. Be polite, not arrogant, but explain your position.
7. Learn not to preach. Teach, don't browbeat.
8. If you have made your arguments, but the clients want something done a certain way, get 'er done the way they want it, and do it well.
9. NEVER denigrate clients or other consultants.
10. Learn when not to accept a job. If you know you cannot adequately do a specific  job, say so. None of us knows everything in IT.
11. Corollary to #10: if you know a guy who can do the job, recommend him or her.
12. Do not start consulting just 5 years out of school.

  13.  There are more than 12 Commandments of Software Consulting. :-)