2) Change a Diaper/Skipping the Line - Kids are not grown ups and they don't have the bladder control that adults have, so expecting them to hold it is a dangerous waiting game; and making a toddler sit in a wet diaper is just cruel. Other people with kids will understand if you ask to skip the line with a wiggling 3 year old; and no one will blame you for changing your infant on a bench.
3) Nurse/Feed their Kids - Similar to the endless bathroom breaks, don't be shy about feeding a hungry kid. You're the parent and kids can't really fend for themselves - so feed them! Also, when children are hungry they get cranky and tend to have more tantrums and meltdowns. So what if you have to cop-a-squat in a stairwell with a slice of pizza; it's better than trying to calm a tired, hungry, cranky kid.
4) Leave Abruptly - You should never feel bad about having to cut a conversation short, leave a cart of groceries in the middle of the aisle, or ditch a party before the cake is served. The reason for your early departure will change - anywhere from tantrums to sick kid - but don't despair over leaving some place when your son is making a scene, needs to nap/eat/potty, or is otherwise just not cooperating.
5) Protect their Children - This covers a wide range of parenting actions from not forcing her to kiss a distant relative she doesn't like, scolding her for running away from you, or questioning a medication prescribed by the doctor. As a parent your job is to assess every situation your child enters and to weigh the experience versus the damage it may do. So never be coy about something you think will not be good for your child's emotional or physical well being.