A constant theme in both my writing and speaking is that of self interest. It's a fundamental component of understanding people and consequently is something that should be reinforced on a regular basis. The better you understand others, the more likely you're going to have a productive interaction.
Remember, nobody gives a rat's rear end about what you want. They're too busy thinking about their own dreams and desires, or at the very least how to deal with the day to day dilemmas that we're all faced with. You might think that this is terribly inconvenient when it comes time to make a persuasive pitch for your own needs, but in fact it's one of the most powerful tools you have at your disposal.
If you've taken the time to know the person you'll be speaking with, then you'll have a very good idea of what they want. No matter how many iterations society goes through, people are still people. If you can help them in their own quest, you're going to immediately make a friend. If you can find a way that your journey comes into harmony with theirs, you'll not only get what you want, you may find that together, the two of you are now an even more powerful force for achieving your common goals.
To train yourself to think in this manner, grab a sticky note and write one simple phrase on it before you post it at eye level on your bathroom mirror. Each morning, when the mirror asks you, "What's in it for me?" just imagine it's the voice of those you want something from.
If you put heart, body and soul into answering that question in a way that would be meaningful to them, your success rate is going to skyrocket. Know who you're dealing with, answer the question on your bathroom mirror, and you'll be well on your way to realizing your own dreams.