Don't tell your hosts on the phone that the only reason you are visiting is to see the children and not you.
Don't bring tons of sweets for the children when your host has told you loads of times that they are trying to stop the dcs eating sweets so much.
Do shower.
Don't tell your hosts that you must come to stay every month and that you will help out and that you are great house guests if it's a big fat lie. You could make a cup of tea, put cups in sink etc.
Do give your hosts some space and stop following them around telling the same old storiess you've been telling for years. If your host is randomly wandering around the garden they are attempting to have a break from you, so don't follow. Try to converse rather than just wait for an opportunity to tell another storey.
Don't talk with your mouth full all the time and then get cross with the children for poi ting it out.
Don't tell the children off for crimes that your hosts don't have an issue with, they are their parents not you and putting too much cereal on their spoons isn't a big deal.
Don't tell the children that their mother is wrong and that it is ok to eat with your fork up, it's not.
Don't leave piles of newspapers, magazines, crap all over the house.
Do put clean sheets on the bed on the rare occasion that your host comes to stay with you.