Approaching Companies For Dealership/Partnership

Were just starting out our business and I feel like approaching companies for dealership or partnership is a downfall for us. What ways you have approached companies in the past? Wrong and right things to say? I normally do my homework on the company before contacting them to see what their all about.

Also when I say dealership I'm wanting to offer their products to my customers. We are in the Agriculture field wanted to clarify don't know if its the same in each field.