A lot of the imagery in this infographic from MagneticNorth.com is business-related, but the truth is that these are all-purpose tactics for negotiating better with bosses, co-workers, roommates, spouses, and your kids alike. For example, one of the simplest pieces of advice (but hardest for most people) they have is "Stay Silent." After someone states their case or offer, ponder it for a few moments without saying anything. The reason it's difficult is the same reason it's effective: human beings hate silence and will usually fill it compulsively, even if means filling it by compromising with you.
Here are 10 very easy-to-learn, if sometimes scary to implement, steps to getting more of what you want without being a jerk: