Making social plans in Brazil requires an extra step.
Without this step, one can expect to be invariably ‘stood up’ without explanation.
After coming up with an idea for, let’s say, nighttime plans with friends (um programa), it is imperative not to assume that you have all agreed on actually doing those plans.
The right thing to do is to ask: “Então, tá combinado?” If you receive a resounding “Combinado!” you can be relatively sure that everyone is on the same page. Once a plan is combinado, it is very poor etiquette to go back on it or to not show up.
To combinar your plans is kind of like an ‘Are you sure?’ button you have to click to confirm an action.