One of the biggest concerns people have when they start an organizing project is where to start. We call it the domino effect.
 
51648948 - row of dominoes in a circle shape on a neutral background
 
There are some clothes in the home office that need to go to the bedroom closet, but the closet is stuffed, so we’d need to make some space in there to put the clothes away. There’s some sporting equipment in the closet that really should go in the garage, but there’s no room in the garage unless we put the bulk supplies in the pantry. But the pantry had a few boxes of paperwork that used to be for current paperwork, but that are now so stuffed that you can’t fit any more paperwork in there and the stuff in the boxes is kind of out of date and could either be recycled or archived in the home office, except there’s no room in the home office unless we take out the extra clothes that should be in the bedroom closet ….
 
It’s like a slide puzzle. And we want to do it with the fewest moves possible. 

pocket sliding fifteen puzzle game isolated on white background. with clipping path

 
Start with making sure you have some space in the room you are working in. So purge (recycle, donate, return, sell) items you know can go. If you need instant gratification to give you some momentum, focus on large items you know you don’t want so you clear the biggest amount of space in a short amount of time. 
 
Stay in one space. Resist the urge to start moving things in other areas. That way your effort will produce the biggest visible return.
 
Once you’ve cleared some space, you can use the space for one category that makes sense in that space. Sometimes that is nothing, and that’s okay. 
 
To extrapolate, to start any overwhelming project, start with a small do-able piece. The start is the most important part. It’s easier to keep up momentum.