In collective bargaining, a win-win strategy is one in which one side comes to the negotiation with a plan for how to give the other side a way to feel like it has won while still getting something for its side. In other words, being ready to compromise and to promote good feelings on both sides is a win-win.
For example, let's say that a union comes into a bargaining situation knowing that the firm really needs to cut costs. The union, however, wants to get higher wages for its workers. The union could come into the bargaining with a proposal for a new contract in which work rules are relaxed so that productivity can increase. When productivity increases, it will be possible for the union to get higher wages for its workers while the firm gets lower costs.
Win-win strategies are those that approach bargaining with this sort of compromise in mind rather than those that approach bargaining with an adversarial attitude.