Take time to organize and take inventory of your supplies. You need to know what you have so you don't end up buying more of the same thing. I have a file of cardstock that fits in a file box, after a while the colors get misplaced and disorganized. If I don't get the colors organized I start buying more of what I already have. When I finally get around to organizing my cardstock by color again, I am always amazed at how much of each color I actually had. When I am more organized it is also easier to find the colors really need to buy. When I am more organized, I am less likely to duplicate my supplies.
When you do go shopping, make a list. If I go to the grocery store without a list, I tend to buy a bunch of great food, but when I go to make dinner I don't have the right ingredients to make anything! I think scrapbooking could be viewed this same way. How many times have you gone to the scrapbook store, and come home with lots of cute things, but when you go to do that "bug in a jar" page of your cute first grader, you don't have anything you need! Make a list !
Have a place for everything. When I start spending more time looking for things than I do creating cards and scrapbook pages, it is time to get more organized. It is important to find specific place for all of your supplies. Depending on your space and what kinds of paper crafts you like to do, you will need different to define space for all of your supplies. For example. Keep all of your writing tools in one location, your glue in another. Things you use more often might be in a pencil box on the counter, and others could be stored in a bookshelf or closet. Some of us have a room to scrapbook in, others have a tote because they scrapbook away form home. What ever your space, try to make it work for you.
Get rid of things you don't use. Most of us have bought tools or items that we either didn't like or are sick of using etc. I have things that I haven't used for a long time or I am sick of them. If you have things that you don't use, maybe it is time to give them a new home. Give it to a friend or family member to try to see if they like it. You could also sell them on an online auction or give them away to charity. Before you buy tools or new products in the future, read the reviews about what others say about them. Other scrappers will give their opinion pretty freely if you just ask. You could also take a class at a local store in order to determine if you would like these tools before you buy them.