Frequently, this does not apply in the staffing industry. When we get positions in, our clients are typcially telling us what the hourly salary would be. However, there is a time and a place for negotiation even with a temp-to-hire opportunity. Once you have been there on a temporaray basis doing a good job and the company is ready to make an offer, use your 3 months experience with the company to negotiate your permanent salary.
Selena Dehne writing for MSN Careers provides some great information in this feature about how not to let fear get in the way of the negotiations. Here is some of the "what not to do" advice.
Mistake #1: Assume that nothing is negotiable.
Mistake #2: Throw in the towel too quickly.
Mistake #3: Say "yes" too soon.
Mistake #4: Negotiate just for money.
Go here to read the full article.