How do I use collaborations with other neighbourhood venues?

A collaboration works when there is a day, a product, or a joint service and both accounts tell it the same way. Tagging each other with no date does not say which door to use. Agree the date, what each place offers, and which frame each account can use. Three venues get tagged on one post and nobody says the day or the dish. You leave with a joint piece that has the date, both doors, and the same text on both accounts.