Negotiating a job offer is not just a discussion of salary and terms. It is a complex process in which you need to present your strengths, understand the employer's constraints and find the best solution for both sides.

Here are 15 key rules that will help you in negotiating a job offer.

1. Remember the importance of likability
It's important to be pleasant to deal with: if people like you, your chances of getting a better offer go up. Be polite and strive for balance when stating your requirements, so you don't come across as greedy or petty.

2. Justify your requests
Don't just state what you want, explain why you deserve it. Your story and reasoning should accompany your proposal.

3. Be ready to cooperate
Show that you are serious about working at this company and that you are not using the offer as a tool to pressure other employers.

4. Understand the other person's motivation
Take into account the interests and concerns of the person you are talking to. Different participants in a negotiation may have different approaches and constraints.

5. Understand the company's constraints
Sometimes a company can't meet all your requests because of internal limitations. It's important to understand where a compromise is possible.

6. Prepare for difficult questions
Be ready for tough questions and answer them honestly, while holding your position and staying attractive as a candidate.

7. Understand why a difficult question is asked
If a question catches you off guard, try to understand its intent and answer with that in mind.

8. Pay attention to the whole package
Don't fixate only on salary. Consider every aspect of the offer: responsibilities, location, growth opportunities and so on.

9. Negotiate several points at once
Propose changes to all points at once, not one at a time. This avoids the impression that you keep adding new demands.

10. Avoid negotiating for the sake of negotiating
There's no need to prove your negotiating skills over trifles. Focus on the aspects that matter to you.

11. Plan the timing of negotiations with several companies
If you are considering several offers, try to synchronize when you receive them. That lets you compare them and choose the best one.

12. Avoid ultimatums
Avoid giving or reacting to ultimatums. Often it's better to ignore them or sidestep them gently.

13. Stay open-minded about the company
Don't take delays in negotiations as hostility. They are often tied to internal processes and don't reflect how the company feels about you.

14. Don't leave the negotiating table
Be ready to continue the dialogue and return to previously unresolved issues. Terms can change over time.

15. Keep your long-term prospects in view
It's important to choose the right job. Job satisfaction depends not only on the terms of the offer, but also on the field, career trajectory, colleagues and management.