Since success for you in a negotiation depends upon the other side's making a decision you want, you should do what you can to make that decision an easy one. Rather than make things difficult for the other side, you want to confront them with a choice that is as painless as possible. 

Here are some considerations to assist you in achieving win-win results:

1. Think like the other side

Who are you negotiating with?

Are you trying to influence a single negotiator, an absent boss, or some committee or other collective decision-making body?

It is best to be able to negotiate with an individual who will at least be able to influence the decision.

2. Identifying precedence

It is never too early in a negotiation to start drafting as an aid to clear thinking. Prepare multiple versions, starting with the simplest possible.

What are some terms that the other party could sign, terms that would be attractive to them as well as to you?

Can you reduce the number of people whose approval would be required?

Can you formulate an agreement that will be easy for them to implement?

The other side will take into account difficulties in carrying out an agreement; you should too.

3. Identify Shared Interests

As a negotiator, you will almost always want to look for solutions that will leave the other side satisfied as well. If the customer feels cheated in a purchase, the store owner has also failed; she may lose a customer and her reputation may suffer.

An outcome in which the other side gets absolutely nothing is worse for you than one which leaves them mollified. In almost every case, your satisfaction depends to a degree on making the other side sufficiently content with an agreement to want to live up to it.

Three points about shared interests are worth remembering:

First, shared interests lie latent in every negotiation. They may not be immediately obvious. Ask yourself: Do we have a shared interest in preserving our relationship? What opportunities lie ahead for cooperation and mutual benefit? What costs would we bear if negotiations broke off? Are there common principles, like a fair price, that we both can respect?

Second, shared interests are opportunities, not godsends. To be of use, you need to make something out of them. It helps to make a shared interest explicit and to formulate it as a shared goal. In other words, make it concrete and future-oriented.

Third, stressing your shared interests can make the negotiation smoother and more amicable. Passengers in a lifeboat afloat in the middle of the ocean with limited rations will subordinate their differences over food in pursuit of their shared interest in getting to shore.