Pull Strings Sparingly
It's always nice to have strings to pull. A previous business relationship or someone you've helped in the past, calling in a favor can be extremely useful, and sometimes necessary. But pull too many strings too often, and you'll find yourself at the end of a rope.
Abusing your influence is unsavory, and the more you do it the more people will pull away. Don't cry wolf and call in big favors on a regular basis, use them sparingly. Do everything you can to accomplish that goal on your own first, and when there's nothing else you can do, pull the string.