I think everyone wants to get organized but getting started is something else. It is a BIG change. I can assure you the discomfort of the process is worth the results.
Things to remember – the stuff didn’t magically get there yesterday so tomorrow it won’t magically go away. What may have been important to you years ago, isn’t now so it is time to align the stuff with you now. I know personally my taste in style has changed over the years. My interests have changed thus what I surround myself with should change too.
So, it will take time. More than you think usually. Block off atleast 2 hrs per week to work on your project. More if you are in a time crunch. Keep your appointments with yourself.
Each item is a decision. Each book on organization you read will give you ideas of where to start. I think the best place to start is the place you use most. The kitchen, living room, office or master bedroom. All have life-changing results depending on your goals (cook more, entertain, pay bills on time, get out the door on time in the morning). Always have a picture in your mind of what that space will be like when you are done.
Two things to remember; touch each item once in the ENTIRE room. I mean everything starting with the visual clutter, then the drawers, then the closet, then under the bed, etc. Everything has to be touched to make it a success. And if you are doing clothing or books and you have more in another space, make sure you address all of that category at the same time even if they are not in the room you are in. This helps with getting organized in your entire home. If you have a hard time with decisions, gather all the books, gather all the office supplies, etc and then do each category when you can see it all. Everyone is different in how they make decisions.
While touching each thing once, you do not need to decide the final resting spot, only if you want it or not. I think this holds people up often because they feel they need to put the keep items away immediately. Wait. Just make the keep/toss decision first.
Lastly, you now have only the keep items present. That is when you look at the stuff and decide where it will be in the room based on if you want it out, reachable, tucked away, in bins, and the like. This is when you think about how you operate and what you prefer.
Recap – you have stuff, it will take time so schedule it, touch each item once, purge, then set up your entire space as you use it and inline with your preferences. So get started!