On to some B's, back to some A's later. As I said, it is a bit of a disorganized A-Z.
The keyboard refuses to type properly so excuse the missing letters here and there.

Backpack: This is your most valuable weapon. A huge backpack will be a big commitment as it is difficult to just leave in a locker and can be cumbersome to carry and put down when you are resting, a small backpack will be too small for the things you need day to day and the inevitable extras that you pick up and are given along the way.

homeless people don't always have a choice of backpack, so ignore my assumption that they do. My first backpack was small and light and too full of heavy stuff bcause I hadn't learned to travel light or stash things. It was a cheap School/college type backpack and the straps dug into my shoulders under the heavy load and made me sick with tension. Then the SVP bought me a new backpack that was slightly bigger and had wide shoulder straps and a waist band that helped to take some of the strain, and I learned to sort my posessions into compartments according to what I needed frequently or what needed to be easily accesible - wash kit, meds, ID, money, first aid kit etc. These things go in th smaller outer pockets, and everything else goes in in order of importance. I keep some things protected or divided in small plastic bags within the backpack.

A good homeless backpack is waterproof or has it's own removable rain cover, it also helps if the backpack has elastic on the back that can be used to secure a spare jumper, blanket or coat, side pockets for flasks or bottles of water and all kinds of other things are helpful, my backpack has side pockets with straps  to keep flasks and bottes secure, and I keep my tin mug attached to one of the side straps. Wide shoulder straps and a waist strap or even a chest strap as well will help with carrying the backpack and keeping the weight even so that you don't get tired or in pain from carrying it.

A backpack also doubles up as a pillow if it is not too big an bulky or full of things that may break or burst under the weight of your head.

I once had a rat right by my head trying to get into my backpack pillow when I was asleep because I had food in my backpack! After that I sprayed deodorant on the backpack when I slept in that particular place. It repels rats.

Some homeless people use trolleys or bags for their posessions, but those are much more tiring and clumsy, in my opinion, hnd carried bags are harder on you to carry all day, and trolleys are not as practical or easy to manouver as they may seem.

I often leave my backpack in a locker for a day if I have a pound coin for the key. Lockers can be found at various libraries, sport venues and daycentres or even art galleries, not everywhere has lockers but if you are lucky and have a coin and a locker place, stash your bag, remember when the venue closes and have time off from carrying weight, it will help your health and wellbeing.

Backpacks get messy and muddled like houses do. Find a private space such as a less used toilet and tip everything out and sort it, you will feel better with the rubbish and jumble gone. Think about what you really need with you and stash or dispose of the rest.

you can get padlocks and alarms for your backpack, I never have, I keep it with me or in a locker all the time.

Finally, don't try to carry your bedding in your backpack, the strain will kill you. Stash it.
I will describe stashing later.

Backpacks are for your personal, precious and day to day posessions. Stash everything else unless you are on the move,in which case carry the rest in separate bags. I know you don't need me to tell you that, cos you aren't stoopid.

Amazingly I hve just come accross 'The homeless guy' on youtube as I looked for a link to do with homeless people's backpacks http://www.youtube.com/watch?v=-quQ-OVJmnk

His actual description of the content of a homeless person's backpack is towards the end of the video but he talks about lockers and usng Wifi in McD's :) he also mentions carrying a change of clothing, I tend to carry a change of socks and underwear and stash and access the rest of my clothing as it is bulky to carry. And just as he says, I carry a variety of toiletries and any necessary paperwork, as well as my meds.