a) Before you collect your children from a hot morning at summer school and promise them a dip in the paddling pool when they get home - check that you actually have one.
b) When making an unscheduled trip to Homebase to purchase a paddling pool, don't bother to ask customer services for the measurements to make sure it will fit on your tiny terrace. They won't have them. And at least 3 people will try to queue jump whilst you are trying to persuade them to find out, convinced that their need for sprockets, loo seats, and a particularly putrid shade of paint are far more important than that of a mummy dealing with two mildly irritated small children who are desparate for a cooling dip in their own palatial Thomas the Tank Engine pool...
c) Always remember to take a lead or similar for Boy #2, to whom DIY stores are places of great wonder, majesty, and a perfect opportunity to get lost.
d) Do not offer said paddling pool experience the day after taking the children to visit a friend in Leafy Surrey who has her own swimming pool. Even a 4 year old can see the difference (though, thank God, mine was too polite to comment on it).