It depends on what level you are teaching but you have to be absolutely ruthless about what you hang on to. There are more wonderful resources out there than you will ever use so you really can’t keep everything. If you have a small file cabinet at home, you can file lesson plans and ideas there. As you do your planning, maintain a file cabinet at school that has maybe 3 weeks worth of lesson plans. Each week carry last week’s home and bring in the lessons for three weeks from now. Have a system for copied material and turned-in homework. The important thing is to keep the clutter under control.
In a way it’s like any other kind of clutter. You can’t keep that beautiful sweater in your drawer just because some day you might lose 30 lbs. You can’t keep can’t keep 3 poofy bridesmaid dresses because they were so expensive. You can’t hold on to every magazine and newspaper until you ‘have time’ to read them thoroughly.
The electronic storage is a good idea but you have the problem of home computer/school computer/back-up media and crashes and compatibility. But subject folders with subfolders for types of files is very convenient. By all means use an electronic gradebook. I keep most of my current stuff on a memory stick and back up to my school computers.
And every summer-clean house and throw away everything you didn’t use last year.