Just to add - I don't do any housework after DD is in bed. There's a lot of 'dead' time to be found between school pickup and bedtime and you can use that time to get things done - school clubs, dinner, bath time, play time, homework, etc.
I usually don't sit down before DD is in bed unless I'm eating dinner, because I use all that time to get the house squared up. It means as soon as she's in bed, I can sit down, shove on Netflix and help myself to a glass of vino 
If I've run her to an after school club in town I'll grab the weekly shopping, get it home and put it away. It takes much less time when you don't have kids with you.
The minute she gets in from school she gives me any paperwork from her school bag - party invites, school reminders, upcoming events, etc. This means her school bag remains tidy and I can spend 5 minutes quickly getting things organised and put in the calendar. As soon as it's in the calendar the paperwork gets put in the recycle bin to stop it mounting up on top of the fridge! On Friday's she knows her gym kit gets put straight in the laundry hamper.
Sort through the post as soon as you hear the letterbox go. Recycle or file things straight away.
It is literally just about getting yourself into little habits and routines. I used to be really disorganised and lazy and the house was a constant tip. I eventually got sick of living like that, went room by room and gutted them all (so important!) and put small things in place to keep on top of it all. It does work. But I cannot stress how important it is to de-clutter. If you don't, all you're doing is moving the mess from room to room. I used to have 1000+ DVD's. Utterly pointless and a total waste of money and space. I have Netflix, Amazon Prime and various other catch up channels I can access through my Prime TV Stick. There was no point in keeping them - I never watched them. So I flogged most of them on Music Magpie, made a few hundred quid and gained a lot of space that no longer gets cluttered or untidy. Same goes for books. I have one bookcase for books now instead of three. I kept my classical literature and collectibles, and sent the rest to the charity shop. If I want to buy a book, I download it to my Kindle. Same for CD's. I have an iPod. Much tidier 