Leave your judgement and advice at the door unless asked for. Also try to remember that helping and taking over are very different things and even the best intentions can be misinterpreted at such an emotional time so I personally think it's best to ask what the new mum would like help with rather than just do it.
As a new mum I got a bit upset in the beginning that I wasn't left to figure out how I was going to be a mum to this new wriggly soft baby that apparently belonged to us now. Everyone told me exactly what I should be doing for everything but it was nice to have the moments where it was ME parenting.. If that makes sense? It's hard to be forceful and stand up for that kind of thing when it's the first go around I guess.