It’s not easy to start an online business from scratch. You probably won’t be able to get to the big names immediately, so you have to look for those smaller suppliers who are looking to expand their business and share the same hunger for success as you do.
You need to present yourself as someone with serious goals who knows what he’s doing and has a plan to get from A to B. The bottom line should be that if they work with you, they will sell lots of products and make money, that’s the bottom line for every supplier really. You need to be legit as well (just like you want them to be).
You need to convey the feeling that you know your stuff, you know how to promote them, you know how to keep customers happy and get return business (not relevant for all types of products).
If you have something to show for it, do it (maybe you have a small B&M business and you want to expand it).