Most negotiations masquerade as fixed-pie situations because people are negotiating about a single issue, usually price. Expand the issues on the table by coming up with a list of issues that are important to you and negotiate looking for joint gains.
Examples here would be: Paid Time off/sick, Retirement contributions/equity, salary and bonuses, and job classification/grade. Identify the priorities then be prepared to make concessions on issues that are least important to you. So what you may do here is say: “I’ve reviewed your offer and I am looking for a salary that is 6% above what you have offered. Also, since I am providing so many years of experience, I would ask to be considered for a promotion after 1 year” - if that is the stuff that is important to you. You can also make up the salary by asking for a bonus or an extra % contribution in the retirement plan.
My advice:
-Be firm but flexible (not a “hard bargainer”)
-Be precise. Don’t say “I’m looking for around $90,000” Say: “I’m looking for $91,000 per year as this is market value for my experience”
-Don't just haggle over salary.