I just got done with a negotiations class last week at work, so let me pull up my notes and see if I can share anything useful. :) Note, the class specifically did not cover salary negotiations, and when I asked the instructor about it, he pretty much admitted that my company didn't want him teaching its employees how to negotiate for salary. That said, I found many things that could be relevant all the same.
To begin with, you need to do your homework. 1) LEVERAGE: This means getting outside industry data on what your job title earns for your education, company size, geographical location, and experience. I use Salary.com and Glassdoor.com myself, though I have found them imperfect in my own situation. Arm yourself with that, your last several performance reviews, your recent significant accomplishments, and what you bring to the new position (relevant experience, etc.).
2) PLANNING GRID: List out everything that is negotiable and rank them in terms of how important they are to you. Examples of items could include salary, # days off, work schedule, remote work or flex schedule, signing bonus, performance bonus, etc. Once you have these ranked in importance, use the research you did above to establish your counteroffer position. The counteroffer should be stretch but realistic. AIM HIGH, but have the data to back yourself up. Your bottom line should be the lowest you are willing to go in each category. Keep in mind that if you get your bottom line for each area, you will still consider this a successful negotiation.
3) For advanced credit, try figuring out what the other side has for their leverage against you and their planning grid. i.e. What factors are most important to the company? If there are things that are very important to you but you suspect are going to be less important or easy for the company to give to you, flag those as negotiation points.
4) When stating your counteroffer, use STRONG language. “I know based on market research that I am worth $x. In order for me to accept your offer, I need you to increase the vacation to four weeks a year.” Don’t use “believe”, “think”, “would like”, or similarly wishy-washy words.
5) When negotiating, make sure to always start by stating your leverage, then follow with your counteroffer. When doing the back-and-forth bit, never GIVE up anything but always trade concessions. As an example, “I can accept the lower salary provided that you increase the sign-on bonus to $10K. Never give up something without getting something in return.
Note: I haven’t tried any of this in real life yet, but the practice scenarios in the class were very useful. I highly recommend role-playing in advance if you think the negotiation will be in person or on the phone. The first role-play we did in class was brutally tough, but by the third time, it was smooth and natural. Good luck and let us know how it goes!