An important thing to bear in mind is that most things are negotiable. Problem is, most people don't ask for a better deal. If your negotiation skills are lacking, buy a good book on negotiation. Or attend a seminar or workshop on effective negotiating skills. Others in your organization with the authority to do deals of any kind should polish their negotiating skills as well.
Negotiation means being a good listener.
It is important to listen for cues from the other party in terms of their key needs in putting together the deal. They might also tip you off in terms of what they would be willing or able to do as far as meeting your terms. Try to avoid tipping your hand in the process. Try to gather information and use it to your advantage. Some business owners and managers believe that a good way to enhance their bottom lines is to pay employees as little as they can possibly get away with.