1. The creative process 2. Archiving/documenting
The amount of paper used in 1. can be very high, but essentially the key point is to let go of all your sketches when you are done distilling them. They are material for the trashbin. This may sound hard but it makes sense when you have a separate step for archiving, which means step 2.
Step 2. means, I distill all the lump of paper into what is required for the project at hand or worth keeping. This depends on the circumstances. Sometimes it means just putting a sheet of paper next to the other bureaucratic stuff, most of the time it means writing a project documentation or "specification" document, sometimes writing an outline for a paper or an abstract. This may be grunt work and the tools may suck, but that's OK since it is separated from the creative process and for the purpose of documentation, not creation.
If you have multiple projects at the same time and find yourself switching around often, make some organized space. There are these stackable plastic things where you can put stacks of paper in, not sure how they are called in english but I do use them to have 3 or 4 separated stacks that I can just pull out or put away when needed.
Maybe the key point is to be able and let go of old stuff. Taking half a hour once a week and browsing through the notes, evaluating and rejecting old/obsolete stuff helps too. Also, the "archiving step" acts as a filter. If you find yourself not having time/incentive to archive a certain idea or sketch, it is probably not worth it and can go to the trash.
Keep in mind, that Ideas (when they are just Ideas) are worthless. They need to be realized and one can only realize so much in a finite amount of time.