Don't give advice unless asked, this includes breezy comments about what you used to do that are posing as advice! If you really want to know the plans re: weaning, sleep, feeding etc say 'what are the guidelines these days' (and don't follow with 'because in my day.../oh, we used to....)
DONT HOG THE BABY! I was adamant I didn't want visitors in hospital, mil came uninvited and stormed into the ward, picked my baby up and didn't let go until we left. This became a pattern for the first 3 months, including when my baby was screaming and she would walk off into a different room so she could have a go at settling her (she is breastfed, she wants milk
). I also used to get my daughter snatched out of my arms before even getting a hello...
Don't take the baby into a different room away from mum. It was like a physical pain to hear her scream, know why, and be powerless to do anything about it because mother in law keeps running away with the baby!
Don't think that helping is offering to hold baby while she breezes round doing housework etc, if you don't want to do housework that's fine but don't try and split the baby from the mother uninvited under a guise of trying to "help". Basically, assume mum will want to be with baby and hold baby and calm baby down unless she says otherwise.
Gahhh, I used to have a great relationship with my mother in law, like literally fantastic, and then dd was born and beyond upset me. Baby is now 4 months and I still can't look her in the eye because I'm so angry about the stuff she did in the early weeks!!
I'm aware that some of the things listed might not seem like a big deal to men or other people but after you have just had a baby there is no accounting for the crazy crazy hormones and that instinct to be connected to your baby!