How to start a family budget? And how to stick to it?

By family budget, do you mean overall household or just groceries? If it is the former, I usually start with a ballpark estimation of how much the household spends in a month. For example, $2000. Then I will make sure that I pay off all the bills and necessities first. With whatever that is left behind, I would divide them according to the other categories like "shopping", "outing" etc. I will put this all in an excel spreadsheet and after establishing a proper estimation, I will ensure that I stick to this figure every month. I make a separate budget for emergencies as I do not want to be caught off-guard during difficult times.