If you're trying to convince people outside clear reporting lines to collaborate with you, you'll need to use your powers of persuasion. This doesn't involve manipulating your colleagues, but rather leading them to a shared solution. Here's how:
Establish credibility. If you have a history of well-informed, sound judgment, your colleagues will trust your expertise. If you've demonstrated that you can work in the best interest of others, your peers will have confidence in your relationships.
Frame goals on common ground. Tangibly describe the mutual benefits.
Vividly reinforce your position. Ordinary evidence won't do. Make numerical data more compelling with examples, stories, and metaphors that have an emotional impact.
Source: Today's Management Tip was adapted from the HBR Guide to Managing Up and Across.