Why not go on the old school of bargaining?
We live in the negotiation age. Nobody knows everything and everybody needs others to reach his or her goal. Neither does a single person has the power to act successfully unilateral in the long run. Remember, you always meet twice in life.
Thus, you have to negotiate with others to get them to help you reach your goals. Hardball bargaining might lead to short term success and definitely to long term defeat (and only, if the other side has no alternatives).

It is possible to reach agreements where both sides win and no party feels deceived. Preparing a negotiation and the very next meeting is the discipline of a professional.

You find more information in Getting To Yes by Roger Fisher, William Ury and Bruce Patton.

And have fun!