I'm not a real Guru in 8051 but I do quote on commercial projects all the time.

Your first criteria is - make money!

1. Do this by firstly calculating all your costs and time required to complete the job, then take the time you allowed and double it.
2. If other people are involved assume they will stuff up or forget something.
3. Most important keep a comprehensive record of the job from begining to end, all faxes, e-mails, drawings and notes from meeting and telephone conversations etc.
4. It hard but try not to cut your costs to win a job as time will nearly allways run out and you need to support your job right through to the final stage and still have something in reserve to cover the FU factor.

Just remember you can do 99 great jobs and 1 bad one and everyone will remember the 1% (especially your competitors).

Tony