Arrange clothes in size order before baby is born
Not just 'Newborn', '0-3' etc. Look at each individual label and arrange by size. For example Tesco's 'newborn' only goes up to 7.5lb and its '0-3' up to 12lb, whereas Mothercare's newborn goes up to 11lb and 0-3 up to 14.5lb. I have wasted a lot of clothes by not sorting them properly and assuming all newborn is the same, and Felix has grown out of them before even wearing them once

Also be prepared to continue doing this sorting every week or two as your baby grows. And don't save the best outfits for special occasions as they grow so quickly they'll end up not wearing them at all!
It's always wind
My Dad told me this before Felix was born but I didn't realise quite how true it is. If they're full and are still complaining, it's probably wind. If they're fussing at the bottle/breast, acting like they're still hungry but won't eat, it's probably wind. If they're OK on your lap and whinge when you lie them down, it's probably wind. If they're clean, dry, warm, fed and generally should be perfectly fine but they're not, it's probably wind. You get the picture.
Baby boys pee everywhere
Be prepared from that first change! They will wee in places you never thought possible. Felix filled his own ear with wee once and we had to tip him up to pour it out

have a muslin handy to dump on top of them and always point their willy down when you change their nappy otherwise when they wee it will shoot out of the top/back/side of their nappy and they will end up with damp patches in the weirdest places and often manage to miss the nappy entirely
Moistness indicator on Pampers
Not to be a brand snob or anything but I found these invaluable, particularly in the early days. The midwives are seemingly obsessed with how often your newborn is peeing and in the early days when they pee such small quantities and well, you just don't particularly know them and their habits and what to look for, the wetness indicator thingy saves a lot of stress (by all means use a different brand but as far as I know Pampers are the only ones that have this at the moment).
Wait 5 minutes after you hear them poop!
I have been pooped on SO MANY times after being a little too eager to change Felix's nappy when it turns out he wasn't quite done. Give them a minute after pooping to maximise the chances of you remaining poo-free.
Don't worry about routine
Your life will be absolute and total chaos for at least the first month, probably two. Don't worry about it. I stressed so much about getting Felix to have a proper bedtime etc etc when he just wasn't ready and neither was I. Until he was just over two months old he was always with us, he'd just sleep in his chair downstairs until we went to bed and then we'd take him up with us. A routine will come naturally eventually. We now do bedtime (a story, a bit of a play, baby massage, a feed) between 7 and 8 and he is asleep by 8 every single night, and has been for a good few weeks now. We had absolutely no routine for ages and he's still taken to it so well so please don't worry about this.
Baby>sleep>food>shower>housework
This one is simple. No matter how much you want to keep the house clean and whatever you will fall into this order of priorities within a week or so as your tiredness takes over. Give in from day one and you will feel so much better! Also stock up on dry shampoo/body wash wipe thingies to make you feel a bit more human when you haven't had chance for a proper wash.
Remember how important your own physical and mental health is
Obviously baby's basic needs come first but remember that if you're physically and mentally exhausted baby won't be getting you at your best either. I can't emphasise how important this one is. I tortured myself to the brink of post natal depression with the whole breastfeeding thing and whilst I am proud of myself for persevering for so long, I do regret it in many ways. They were Felix's first precious few weeks and I spent them in utter misery, and I can never get that back. When it comes to #2 I will give it a fair go but also be happy to give up much sooner. Try your best to take yourself outside of that very intense experience of having a brand new baby and look at the bigger picture. I would rather have had a baby on formula and enjoyed those first weeks more. But at the same time hindsight is always 20:20 and you can only do your best. As long as you and your baby are healthy and happy you are doing amazingly and try not to feel bad about any of your decisions.
Don't panic about sex
It will be OK! I tore quite badly (oh yeah, and it turns out when the midwife is stitching you up and you ask how bad it is they lie to you! My notes and my own poking and prodding about down there said I'd torn a lot worse/had a lot more stitches than she told me I had at the time) and had sex 5 weeks later. It was quite uncomfortable but a few times after that it was absolutely fine and now I can't tell any difference apart from (TMI) still being a little bit dry due to the hormonal changes. My OH says it doesn't feel any different either so I just hope he's telling the truth
Don't clear out your maternity stuff just yet
I am STILL in my maternity clothes

Also if you have any under-bump trousers or PJ bottoms keep them in case you end up with a C-Section. At the moment I don't even bother putting my clothes away as my shape is still changing daily. I just have piles of clothes all round the house which I try on and update every week or so

It seems to be working for me but then I'm a lazy git and hate hate hate putting clothes away.
Don't be surprised if you feel very broody very soon
If your birth went as planned, you may well be excited to do it all again as it was amazing. If it didn't go as you'd hoped, you will probably feel you can't wait to do it all again 'properly'. I am broodier now than I ever was when WTT and am seriously having to rein it in. I suggest getting a type of contraception that you have to go to the doctor to have removed

I have the implant now and wouldn't trust myself/us to be using something self-administered!
And finally, my #1 top tip - enjoy it!
There will be moments where it feels like hell on earth. There will be moments where you think 'what the hell was I thinking?' and think you're not cut out to be a mother. You will get through it and this is totally normal. But enjoy those cuddles, take lots of pictures and make the most of them being so tiny. You will never ever experience the first few weeks of being a first time parent ever again and it is incredible. When you look back you will remember this time with joy. Even now only 3 months on it is like I have forgotten the absolute chaos of the first month or two and I can't picture our lives without him like he is now. Those desperate tearful nights when you don't know why they're crying and you just want to sleep will be forgotten or at least will pale into insignificance, very soon, I promise. Before you know it they will be smiling, giggling, crawling, walking... in those first weeks when everyone tells you it goes so fast and you're just hoping to get through the day so you can go back to sleep you won't believe them, but it's so true. Every day brings its challenges and rewards but you will still miss each stage that has passed so treasure it.
I am so jealous of you ladies embarking on the adventure of a lifetime. I can't tell you how much I would love to go back and do it all again but of course I'm so happy to be where we are now. I know I'm no expert having just got a 3 month old myself but if there's anything at all I can do or any questions I can answer I'll try my best. I felt terribly lonely in the beginning, don't know what I'd have done without this place and I'd love to be able to help someone else out the way others have helped me
