Moonshaped you're bound to feel somewhat overwhelmed. It’s a big thing you’re doing.
Do you know what you don't want to pack up? Sometimes putting that to one side or even into boxes temporally (labelled!) can help.
For my sins I box up stuff in and out of storage quite often and am an over organized hoarder so hopefully something out of what follows might help. If not please just ignore.
Photographs, labels and lists are my friends, along with a special place to keep a folder of lists and important documents. Find a place where it lives for now, and stick to it. Regardless of it you make lists on a computer, or paper, photograph them. Whatever goes down there’s a good chance you’ll have your phone.
Apart from good boxes preferably the same size/s, Pound-land labels, brown tape, permanent marker, and colored felt tips are really helpful. Bubble wrap or lots of newspaper if possible. Label 2 corners of each box so that no matter which way round the box is placed, you can always see one of the labels. Bit of brown tape with a thick arrow, so boxes stay the right way up. (possibly a bigger deal when moving place)
Writing everything on labels and lists, feels slow, but it saves so much time and stress later. (please remind me to listen to myself!)
I also colour code categories on labels with felt tip pens. So all Kitchen stuff - yellow, Bedroom -pink, bathroom - blue, garden or plant related - green etc.
For most people packing rules are don't mix things from different rooms, but for some of us that doesn't work because things weren't in the right rooms in the first place, so IMO putting like with like is a far better method.
Think about weight ie if you have a lot of books etc, pack them up first so they are the bottom stack. This can cause issues if other things are in front of them, but although it’s double handling, sometimes just moving stuff out of the way, packing books, then putting the shifted stuff onto the shelves to make space, until you’re ready to allocate them to boxes, can work.
Clothes and bedding, if you’re expecting to still be packed up in late Autumn, think about what you’ll need then, and pack it together clearly labelled and kept near the top of any clothes/bedding stack. Hot water bottles/electric blanket, gloves, thicker socks, might want to go in this box too. You may want a specific box for tinned packet goods with short expiry dates.
If you have to use sacks, double bag contents and tape. They get damaged moving around.
One way of thinking about random stuff is what category does it go under?
So is it decorative, entertainment, specifically Christmas, deeply sentimental (the stuff you’d grab in a flood or fire) or spares and repairs, tools, maintenance, practical comfort (ie cushions, lamps, hangers) stationary, cleaning, household gadgets, projects, art, sewing, 'office,' gift box, possibly even donate box, etc.
Follow you’re heart rather than how you think a thing should be thought of, because that way it’s easier to retrace were you would have packed it.Ie: a framed photo might be decorative, but it may well actually belong in the deeply sentimental box.
A rubbish sack, and a recycling sack, close by always helps even if it’s just for old envelopes, or dead sticky tape.
Which room/cupboard/hall/corridor would each item live in if things were organized as you'd like them?
So you might well have an office area in your living room, and jewellery would probably live in the bedroom, but might go in the specials box, but hair care or sunscreen could be bedroom or bathroom, dependent on individual choice.
This way if you end up with smaller boxes on top of stacks, they will hopefully be correctly colour coded to the right room (as well as contents listed) regardless of category.
If you don’t have an office, shed, garage,or cupboard under the stairs, etc, for now imagine you do.
If you can’t decide on a category, maybe ask on here, or create a ‘totally random’ box. I hope all that makes some sense.