Congrats all that are expecting...
I just had my first son on Sunday, so very newly home... But I have been a step father since my 3 year old was 6 months old... so I have done most things, just not the birth or early part.
Advice from me is fairly similar to Wyld's...
1. Do everything you can to help out, it makes things easier on everyone.
2. Sleep will be deprived, but it is well worth it, seeing the smiles, bruises, cuts, injuries, laughs, and just random things of kids is great.
3. Let them play and do everything they can. Let them fall over, and eat random things, but always keep them healthy. No matter what dog poo is not healthy!
4. Enjoy every moment!
5. Allow time for yourself and let your partner have some time to themselves. Sometimes all you need is an hour of solitude
But mostly, just go with the flow, and parent your style, don't let people tell you how to do things when you think its wrong. Advice is one thing, but telling you how to do things is another.
And just be thankful that you aren't like me with 2 kids with the same birthday 3 years apart. Which means an 18th and 21st on the same night to come.