1. How to agree on what kind of license they are buying? Is it part of the site or a conversation?
I would make it part of the functionality of the store site (I don’t do that on ours).
2. How do they receive your important information (contact info, BMI/ASCAP account number so you get royalties)? Do you send them a pdf? Include the metadata in your audio file?
It’s included in the invoice they receive from us.
3. Did you consult a lawyer beforehand? Why?
No, poked around other sites to see what their terms of service were and created my own. They can’t check out until agreeing to them.