Put it in writing without it feeling like a contract
It isn't a contract, it's a note that prevents arguments
A lot of people running a small shop avoid putting things in writing because they think it cools the relationship down, or that it takes a lawyer. The opposite is true: what cools a relationship down is discovering halfway through that each of you understood something different.
You don't need legal language. You need a ten-line message both sides can reread, written in the same chat where you're already talking, using the same words you'd use in person.
1. What exactly is going to be done
Format and quantity. "One short video and two stories" is specific. "Content about the shop" isn't. Add where it gets posted, because one account and three accounts are not the same thing.
If something absolutely has to appear — the name spelled correctly, the address, one particular product — say so here. It's far easier to include it up front than to ask for it afterwards.
2. When
Two dates are usually enough: when it's made and when it goes out. If the exact publishing day doesn't matter to you, say that too; it helps the other person to know they have room.
And a third if it applies: how long it stays up. The answer is nearly always "it stays", but if you're expecting it to stay, write it down.
3. What each side gets
This is where people go quiet, and it's exactly where they shouldn't. Whether it's money, product, a service or a mix, write it as clearly as everything else, and include when it's paid or when it's handed over.
If there are costs involved (travel, materials, something that has to be bought), say who covers them. It's one line and it saves an awkward conversation.
4. What you can do with the content
One point, three details: where you'll use it, for how long, and whether you'll credit the person who made it. If at some stage you want to use it in paid advertising, say so from the start, because for most people that's a different thing altogether.
And the other way round: if there's something you'd rather wasn't shown (the back room, a supplier, someone on your team's face), this is the place to say it, not on the day of filming.
5. What happens if something falls through
Nobody plans to cancel, but cancellations happen: illness, something unexpected, roadworks outside. A line like "if anything comes up for either of us, we say so as soon as we can and find another day" settles the vast majority of these cases without drama and without anyone feeling bad.
Where to put it in writing
Wherever you're already talking. A message that starts with "here's a summary of what we agreed, tell me if it looks right" and ends with a "yes" from the other side is enough for almost everything. Email is even better, because months later it's easier to find.
What doesn't work is leaving it in a phone call. Not out of distrust: two busy people's memories drift apart within days, and after that neither of you has any way to check who remembered correctly.
The one thing to take away
Write the summary yourself, as soon as you hang up or they leave the shop, and send it the same day. Whoever writes it fixes the terms without imposing anything, because the other side only has to confirm or correct. It's the cheapest possible way to make sure a collaboration ends well.