h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

The best idea is to move a long way from your relatives. That way you can always find an excuse:

The car's in the shop.
I have to work.
My spouse has to work.
The child has some activity that can't be cancelled.
The cat has to go to the vet.
We're all ill.

If you have to attend:

Stay at your in-laws. That way you can escape, and you're not trapped at your relative's place.

Threaten your child/children with sudden and violent death if they even consider stepping out of line. Warn them ahead of time about any cuddly relatives or embarrassing comments that might be directed at them. Be specific - you WILL stay out of Grandpa's garage, you WILL NOT tear all over the place with your cousins, you WILL speak politely to the relatives, what's in ANYONE'S CAR is NONE OF YOUR BUSINESS! (see below).

Dress conservatively. Where your parents might only be embarrassed by your blue jeans, Drop Dead sweatshirt, or short-shorts, the old Aunties will talk about you around the family for years. And while you're at it, make sure Junior isn't wearing that trendy but obsene t-shirt, and has washed the green out of his hair, or dyed it a conservative black.

If the part of the family who don't drink will look down their noses at you, before-hand, hide your bottle in Dad's garage, or the trunk of your brother's car, so you can slip away for a nip when it gets to be too much. Chances are, all your cousins will trot out their booze when they see you coming!

Sorry Barney, but what century are you living in? If everyone just acts normally they shouldn't have any problems. If your rels get to talk about some good Tshirts and interesting hair it will probably brighten their life.

Yes, but some of us have elderly relatives, that definitely live in the past. They can remember you in a hat and white glove for church, and just can't understand trendy! I'm living in this century, old relatives aren't!