Get it in writing every time. A solid UGC contract covers the deliverables and format, how many revisions are included, the fee and payment terms, and the big one, usage rights: what the brand can use the content for, on which channels, and for how long. Cap perpetual all-channel usage or charge for it. Note any exclusivity and who keeps the raw files. This is general info, not legal advice, but never hand over content on a verbal yes.
Always in writing
A verbal yes is worth nothing the moment usage or payment gets disputed.
Pin down usage rights
Where, how and for how long can they use it? This is where UGC creators lose money.
Cap the revisions
Include a set number. Unlimited revisions is unpaid work waiting to happen.
Note the raw files
State whether the brand gets your raw footage or only the final cut.