When you see a frazzled parent counting their pennies because their toddler is demanding a drink AND chocolate, instead of commenting that they should learn to get what they're given - See if you can afford to help them buy the drink, you don't know how thirsty the toddler is and whether the chocolate was promised for walking instead of being carried or just because the parent didn't realise they had no money left and had left their bank card at home.
When you see a little girl running around with wild hair whose mother says she won't let her brush it, instead of commenting that YOUR child knows she has to do as she's told - Tell the mother it doesn't matter, it's not the end of the world, you haven't tried to get that particular child to have their hair brushed and you don't know how hard it might be.
When you see a Mama crying because their 4 year old child just plain won't budge and it's raining and their 9 year old is getting stressed and the baby is crying, instead of telling them it's their fault the children are like they are - Give the Mama a hug, give the 4 year old an incentive, tell the 9 year old they are doing a super job of looking after their baby brother, and offer to help them get home.
When somebody tells you they just can't work because their child just doesn't "do" childcare, instead of snapping that some people HAVE to make tough decisions - Believe them, not all children are the same, and they have probably worked with other children and DO know what it's like to juggle work, childcare and a house, quite possibly all by themselves without a partner, and even more likely feel guilty and like they have to justify themselves every single day.
When a Mama tells you they need some time out, a break, to feel less like a human climbing frame, instead of telling them that they should want to constantly be with their child otherwise they don't love them enough - Tell them that everybody feels that way sometimes, there's no need to feel guilty, and it's ok to need to feel un-mauled every now and again.
When you walk in a house where children live, instead of commenting on the mess - Be honest about how messy your own house is or how it would be if you had children, no cleaner, and hadn't slept in 4 years. If there is only one untidy room, do NOT focus on that one room, even jokingly.
Most of all, when you see a parent struggling, instead of judging, see what you can do to help. There are enough people in this world judging parents without us turning on each other. There is no such thing as a perfect parent - if you know you are doing it wrong, then at least you care enough to be bothered about whether or not you are doing it right........and as we tell our children, the most important thing is that you try your best, because sometimes, that just has to be good enough.