Throw everything away except for tools and bike/parts and start over.
Yeah right, wish I could do that.
The only way I've figured to get a handle on it of any kind is to let go of any sentimental value the stuff has and pitch it if I have no definite plan to put it to use in the very near future.
Example is...I bought a new bath faucet kit which came with the new drain pieces. I have no plan to use the drain parts so out it goes.
After that is start separating everything I haven't used or had a use for in the last year.
Set that stuff aside for sale or trash.
It is hard to get rid of good stuff but it's the only way if there isn't room for it.
Of course as soon as I get rid of it I need it 2 days later.
For the rest of the stuff......floor to ceiling shelves. Get everything off the floor. Designate shelf areas to different categories like oil and car stuff here, Bike parts there, Household there.
If there isn't enough room for everything off the floor, time to get rid of more.
All sounds good in theory......I should talk. Should see my garage and yard.
Oh, hang stuff from the rafters and walls like shovels, rakes, weed wackers.
Surprising how much room that stuff takes when standing in the corner.