Ask HN: Advice on getting brands to sell on your store

Hi I'm making a new account to post this question, as people sometimes do.

My startup involves an online store selling some products. It has tremendous benefits over existing channels so I'm not very concerned about selling the merits of the idea. I know how to present it's usefulness from the clients's perspective.

As a hacker I found coding the the site easy. But I have no business side co-founder. So as a total noob to business I'm just looking for advice so I don't embarrass myself.

Specific questions I have:

Are the any general business decorum I should know about when presenting the idea (phone) to a company.

How important is the written proposal. I assume if a brand is used to selling with many retailers it will be easy, but on the other hand a smaller brand might have more requirements?

If the client is international, how feasible is getting a deal without flying there and shaking hands.

Am I over thinking this and this will actually be way easier than I thought.

Are there any general advice you might have for me.

Thanks HN