What to do if you see a child who has an asthma attack?

Very broad question: There is little to do for an acute attack without administering medications. The best approach is to get the child to calm down (good luck!) and try exhaling through pursed lips like blowing up a balloon. This creates enough air pressure in the lungs to keep the airways open. The parents should have albuterol or an epi-pen; if they're not around, call 911.