I spend alot of time relocating things in clients homes. When people run out of space, they tend to shove things anywhere they will fit. My rule of thumb is put like with like. I know that you have to be extra creative with the "small city" space that most of us have.
Its important to use all your space. Time after time I find basements aren't getting utlized. The attic is empty. Storage is a mish mash of items from long ago.
Most of the time when I start working with a new client, I start with their storage unit or area. Its important to make some space and purge what you don't need. Its always amazing how many items can be released from storage. I always hear phrases of "I didn't know I had that".
Depending on where you live, you have cold storage and warm storage. Cold storage is totally out of the way. In a home cold storage is defined as an attic, basement, or crawl space under the stairs. In a condo, this would be your storage unit in the basement or storage room.
So what should your put in your "cold" or less accessible storage? Memory items are a good bet. Holiday items that you only use once a year should also go in cold storage. Anything that you don't use or only use a few times per year. If you only travel once or twice a year, take that luggage out of your closet and store it as well. Old archived taxes and mortgage papers can stored here as well. Seasonal items (ravinia or picnic stuff) should find a home.
In order to have your storage be effective, the bins or boxes should stack nicely together. I prefer clear bins. Also make sure that everything is labeled.
Warm storage as we call it, includes space such as a extra closet, crawl spaces ect. It is space that you can reach pretty easily. So what should you put in your warm storage area? Anything that you use regularly or on a semi-regular basis. If you don't have a linen closet, put your extra linens here. Some of my clients bin up their winter boots and coats to store. If you travel frequently, this might be a good place for your luggage. Using part of your warm storage area also works for pantry (costco) overflow.
The bottom line is to determine what you use and what you don't use as much. With this simple guideline, you will be able to decide where you should store it.