A few years ago I helped to organize our Children's Theatre costume shop and our system really works!  We got a local business to donate $300 towards  the purchase of  clear storage bins with locking handles in the lid.  They are all uniform in size.  We lined them up and started to sort into the bins.  For instance, we had three bins of vests--one fantasy/period, one manufactured vests, and one that had multiples (ones that we made that had five or six or more that were exactly alike) .  We did this with every catagory of clothing.  We then labeled each box with PRINTED LABELS (not handwritten--this gets to be junky looking-and invites putting things back improperly or hapazardly) Next we put all of the bins on shelves by type ie: all the accessory bins together, all hat bins next to each other and so forth.  Our next step was to numbers on the bins in order on the shelves.  We have around 120 bins.  Then we inventoried the bins by type and number. Now when you want, let's say, an ascot you look on our sheets for accessories and then men's neckwear and you see that ascots are in bin 12.  You look at the wall of bins and in bin 12 are ascots!  Amazing!  It also makes it really easy to put things away and you don't keep buying the same things over and over because you can't find them.  Also, the bins are put back in place because most of the population know their numbers and can put them back in order. (This is not true of all people--especially some teenagers!:)  We have had this system in place for four years and it really has worked well.  It also didn't really take that long to do.  Get about 5-6 people and a few nights and it can go pretty quickly.  We actually took everything outside to sort.  It is also a good time to get rid of the junk that always creeps in.  Get all of your costumers together so they can decide TOGETHER what is junk and what is not.  As a costumer I know it is hard to give up something that took you hours and hours to build--but a chicken-wire bird costume that you used ten years ago for Alice in Wonderland probably has 'seen its day'.  If everyone does it together you can kid each other into giving up the 'things that must go'.