What are some basic tips for working with consulting / staffing agencies? In the IT industry I have seen many BAs who are hired through an outside staffing company as contractors. They work hourly, have limited benefits, etc. I am sure there are benefits and flexibility to this, so I am wondering what tips there are to ensure the best deal for the contractor?

For example, how to negotiate wages, travel reimbursement etc? For someone new to the industry, what are the things you would recommend they look out for during the hiring / interview process?