Always pack up seasonal decorations and supplies neatly before storing them in the basement, attic, or garage. Be sure to properly label them so they're easy to find next year. And use a system to help identify bins you need more often than others (like a sliding scale from 1 to 3, or A to C.) Place "A"s or "1"s in the easiest-to-reach areas, while "3"s or "C"s can be a little further away.
Ask yourself what you and your family absolutely need. Donate anything that you don't want or need or have doubles of, and toss anything that's broken.
Identify the bad habits that are stopping you from being organized and create solutions to solve these specific issues. For example, if mail piling up on your kitchen table is a problem, then try adding a recycling bin to your entryway.
Give everything in your home its proper place. This will make it easy to always put things back where they belong. And the items that have no place? You probably don't need them at all.
Keep like-things together to make it easier to keep track of what you have and what you need.
The things you use most often, or should be using more often, need to be at your fingertips. Use "active storage" for these items. This could mean a small bowl by the entryway for keys and sunglasses, or a canister on the kitchen counter for scissors and other tools you use a lot.
Whether it's hanging file folders, storage boxes or digital files on the computer, label everything as clearly as possible so you don't wind up spending time down the road re-opening things to discern what's inside.