Find a simple system that works for YOU, and stick with it. A storage unit can be anything -- a cardboard box, plastic file box, or a nice wooden file cabinet. What you use isn't as important as actually using it, and sticking with it.
Store your important records in a RED hanging file folder so you can find them in a hurry.
Do your filing once a month. Keep the records in an attractive basket until ready for filing; this will provide a place to put them so they don't end up accidently getting tossed out with the trash.
When cleaning out a drawer or closet, empty out its entire contents and begin sorting them into 3 piles: stuff to keep, stuff to throw away, and stuff to give away. Put the stuff-to-keep pile back into the drawer or closet, and toss out or give away the other piles. (Source: Simply Organized by Emilie Barnes.)
Break down big projects into small tasks. Instead of cleaning out and reorganizing the entire kitchen in one day, do just one cabinet or drawer each day. Or, fill just one grocery bag with old clothes you haven't worn for two years.
Don't just lay it down... put it away! It takes just a few moments longer to put something where it belongs, but it can take half a day (or more) to put it all away if you lay it down just anywhere and forget about it. Learning to put things away eventually becomes the habit if you consistently do it. Say to yourself "no, don't just lay it down, put it away". You'll be rewarded with a lot less clutter!