I think planning is a great suggestion. Even just things like, what will your return policy be or what is your responsibilty regarding returns? How much product will you be able to carry? How will it arrive in a store? Who pays for the shipping ( I realize it's local but can you deliver large orders? Will you drop ship?? What's the minimum order quantity? Will there be one? Where is your product made? Specific consignment terms. Is your profit in dollars worththe time/effort? A question I fudged over about when I started my business.
I used to sell musical instruments and when someone came into my store unprepared I wouldn't work with them. The headaches in "training them" far outweigh the benefit of their product. I would also bin any emails that I didn't sign up for. I think face to face is the best approach then they will get to see your passion for your idea, something that is very difficult to convey in a letter of email. If they are local then you'll be able to say "you're in the area, you get their business" which is something an email can't convey.
Which ever method you chose I would recommend the "what's in it for them?" be the main focus.
Okay, there's a little babbling going on there lol. Good Luck!