The first job for a key costumer in the office will be unpacking and documenting costumes from Hollywood. If it's a period show, that could mean many e-crates. Even if it's contemporary the designer has usually had fittings with principles or shopped the favorite L.A. stores.
The warehouse organization is determined by the script and laid out by the supervisor. There will be fitting areas, washers and dryers, costumers desks, an aging and dyeing area and a seamstress area. There may be more or less, but access between all the areas so racks can be rolled is important.
Clothes are hung on racks separated between principal and stock. When the boxes are unpacked, there will be paperwork to compare with the contents. Anything that does not match exactly needs to be noted. Things will be grouped together in size order, usually mens/womens. If it is a period show that covers more than one time, the different periods will usually be grouped together. Uniforms and sometimes specialty costumes are usually broken out separately.
A receiving and shipping area around the desks needs to exist. Things coming in need to be tagged as to what character or closet they belong. Shopping sometimes has a time limit when returns are possible and that needs to be clearly noted. After a fitting there are usually costumes to bag and clothes with receipts to return. Returns need to be broken out by store with the return by date clearly visible. PAs can do returns, but they must be sorted and bagged by a costumer. Sometimes there is an assistant designer, but all principal fittings need photos taken with any notes, alterations pinned and noted, changes bagged with rejects grouped to return.
As much as possible, after a fitting a tag can be created listing Actor's name, role, change number with scenes working and a brief description of the clothes. Any alterations go to the seamstress with a different colored tag listing role, change number and date working along with the alteration note. Once the costume is complete and tagged it is ready for transportation to the truck. Nothing should go to or from the truck without an identifying tag.
When it comes to background fittings, stock will need to be pulled and organized in the bg fitting area. If minors are involved, there should be four dressing rooms. Most of the continuity programs allow for tags to be printed with scene, role and such. There should be room to write in the artists name. Once the outfit is chosen, it should be bagged and tagged and placed with the other costumes for the scene. As far as organizing fitted costumes by number or name, the background artist will not forget their names. There will be pictures taken and sent for approval with a labeling process.
The costumes after fittings will probably need to be transported by a stake bed truck with transportation. A single principle change can be done with the daily Transpo trip between the office and set, but even then there may be enough for a van ride. Fitted costumes should not be transported in personal vehicles for insurance reasons.
There should be a wrap area and costumes should go there not long after that actor has finished. As much as possible the costume should be prepared like it is ready to go into the wrap box for storage. If there are rentals, after picture wrap the rental items will have to be pulled and noted. They will then go back to the houses in a separate hold box. Other boxes go to wherever the producers want and there will be leftover office supplies and sometimes clothing stock that need to go somewhere useful.