Systems and routine are key to being organised.
I have a 5x5 kallax unit when you come in my front door. The top row has boxes where we keep practical stuff - bulbs, torches and candles/DIY tools/First Aid stuff/batteries and electrical stuff like extra cables and power banks/general random junk. The middle column I then use for decorative stuff in two cubes and then the bottom two are stuff like hats/scarves/gloves/ umbrellas/shopping bags etc that you always need on the way out and then DD has two columns and I have two columns for stuff.
One of my columns is for daily stuff - shoes in the bottom two cubes; anything I need to take out with me the following day (eg books to be returned to the library; parcel to take to the post office etc) in the next one up; my daily hand bag in the next one and my gym bag in the top one. The other 3 cubes I use for admin - one is for mail to be dealt with, whether that's letters that have come through the letter box or letters from DDs school/extra curriculars; one is for stuff I need to keep but don't need to do anything with (eg bank statements, annual council tax statement or policy renewals) that I just dump in a storage box and then sort through a couple of times a year and file into long term storage/shred as appropriate and the last is for recycling - so junk mail/take away menus/ opened envelopes etc so that that stuff doesn't ever enter the house to be left lying around; I open mail in the hall, it gets put in either one of the keep cubes or straight into the recycling box, that way there aren't piles of post randomly everywhere.
DD uses hers where one column is for school stuff - her school bag/lunch bag and water bottle/any extra curricular supplies/shoes - and the other column is stuff for her clubs - flute case and sheet music folder for both flute and guitar/work book and folder for Spanish class/dance bag for dance class/drama stuff for drama class. All the club stuff lives there permanently so when she comes home from class, unless something needs washing (in which case it gets washed and put back immediately) everything goes back into the relevant cube. Her school stuff has to be there before bed every night. She has a whiteboard with her weekly schedule on the wall in her room so every night after she finishes her homework she brings her school bag down along with anything that needs to go to school the following day and it goes in the relevant cube; her lunch bag and water bottle goes on the shelf with everything packed except her sandwich/fridge stuff (which live in a specific place in the fridge) so all she has to do in the morning is add that to her lunch bag on the way out. I can just glance at the unit and see if there are any gaps but it's just second nature for us both to put everything in the unit before bed so stuff is ready to just grab and go in the morning and there's no looking for sports kit/lunch bag/permission slips etc on the way out of the door.
Every Sunday evening I sit down and organise for the week ahead. This is when I take anything from my "admin cube" at the front door and put it in the diary or confirm it's already diarised and then file/bin the actual letters. When DD is with me (I share 50/50 custody with ExDH so she's here every other week) we do it together after dinner, when it's just me I take 20 mins with my diary in front of the TV. If there's anything for DD then ExDH and I have a WhatsApp chat we use just for DD "updates" and if we get letters for events etc then we take a photo of the physical letter and add it to the chat, that way we both have a copy (eg a letter might come to my house for an appointment happening on ExDHs week so he needs the info) and also so we can refer back to it without having to have the physical letter lying around at one house or the other. It isn't like a formal meeting, we just sit and discuss what's coming up that week to make sure nothing is forgotten.
I take my diary and make sure everything is diarised for the week. I have a diary where the week is on one page and the other side is a notes page so I can write everything - appointments, to do lists, notes, meal plans, shopping lists etc - in one place.
On Sunday evening I go through the upcoming week, any appointments are on the diary page and then I add in anything I need to do on specific days (eg if I need to order a repeat prescription I put it in a specific day rather than on my general to do list so I know it will be ordered in time to collect before I run out) and then general stuff just goes in a general to do list to be done as and when I get a few minutes. I try to add a few declutter tasks every week but they're little things eg sort top drawer in bedside table; go through pens and bin any leaky/empty/dried up ones etc
I also schedule in two weekends every year to do a deep clean - I tend to do one at the end of March and one at the end of October - where I take two days to do a proper "spring clean and sort". On those two weekends I book nothing else in and just focus on the house. I use those days to move furniture, clean the oven, wash the cushion covers and generally clean everything, pull wardrobes out and sort all the clothes for what's to be kept and what's to be donated (I switch out the bulk of my summer/winter wardrobes on those weekends so in March I put away most of my heavy winter stuff and on October I put away all the summer dresses and sandals, anything I haven't worn that season goes on the charity pile) etc. I also get DD to go through her stuff and get rid of anything broken/damaged; donate anything she doesn't use or has grown out of and generally organise her room.
Because that time is booked in and an event in my diary I find I respect it more than when I just say "Oh I'll do XYZ one weekend" and then put it off because I have agreed to do something else.