1. The Closet
A lot of people nowadays are delegating a section of their closets to cosplay. I personally have a sewing room with a large closet that I use to house most of my costumes. With my longer costumes, I like to put them in clear garment bags on large plastic hangers. This allows the fabric to drape naturally without any bunching or crumpling at the bottom, so it can hang neatly in the closet. The clear garment bags allow me to see which costumes are which just by looking at them - great for when you just have to grab a costume and run! I also like to keep all the accessories for a costume with the garment itself: belts, jewelry, gloves, capes, head pieces, etc. That way, I don't have to look all over my very messy room for them if I need the costume together in a hurry. They all fit into the bottom of the garment bag with ease, and can be kept in smaller bags or boxes for organization.
If you have a compact garment, or something that would be easier to store folded away, you can buy garment boxes, large RubberMaid containers or storage boxes, large gift bags, or hat boxes. I have several costumes folded away, complete with shoes and accessories, in clear plastic storage containers and pretty gift bags. Again, you can easily identify the costume just by looking at the box or bag, and it can hold all parts of your costume for easy retrieval. You can also use a separate dresser solely for cosplay costumes and accessories if you have the room to spare. Each drawer can be allocated to tops, bottoms, small pieces, footwear, and so on, or even to specific costumes if you so choose.
The only thing I recommend keeping separate are wigs, large shoes, and props. I store my non-styled wigs in their respective wig bags in a large hat box. My styled wigs that cannot be laid flat are stored on wig heads on shelves in my sewing room. It's important to keep your wigs neat and safely stored where they cannot be tangled, mixed up with objects that could stain or damage them, and away from heat or water. Props also need a separate place to call their home. I can't exactly fit a sword, a few flails, armor, and helmets in a garment bag along with the costume. Again, longer plastic boxes with lids, wig heads, and other such containers are ideal for protecting your props and storing them. And since shoes can be all shapes and sizes (and have all sorts of nasty stuff on their soles), it stands to reason that pirate boots might need a whole corner to themselves, while sandals and flats can be stored in smaller shoe boxes.
2. Maintenance
So, now that your costumes are neatly organized and stored away, it's a good idea to perform maintenance on them from time to time. Remember the last time you wore a costume and noticed that one of the seams was coming undone, or you had a ketchup stain on the lapel, or it smelled a little stale? Well, it's important to keep your costumes clean and fixed in order to extend its life. If taken care of, a well made costume could last for years!
After wearing a costume, you might want to wash it. Depending on how detailed the costume is, this process will vary greatly. While you can hand wash Inu Yasha's robes or throw it in the washing machine on delicate cycle, you can't exactly throw a Trinity Blood costume in the wash. For detailed costumes, spot cleansing with a washcloth is great for cleaning up stains and spots, and then misting with a coat of Febreeze helps to freshen the costume up and get rid of any unwanted odors. Simpler costumes without much detail are generally okay to hand wash or machine wash on delicate and then hang to dry. I don't recommend putting a costume in the dryer unless you have preshrunk the fabric - it's too easy for the fabric to pill up, shrink, or become otherwise damaged (I'm also a huge worrywart ^.^ ).
Checking your seams and detailing is also an important part of a costume's upkeep. If you notice fraying edges, re-sew the edges or apply Fray Check to stop the fabric from coming apart. If you see a grommet ripping out, apply some fabric glue around the grommet to restabilize it. If beads are missing, or paint is chipping off, reapply the details to keep them looking their best. Remember, you want your costume to look fantastic regardless of how old or well worn it is.
Another very important step is to make sure you iron your costume!! Nothing is more dissapointing than seeing a great costume covered in wrinkles. Take your time and iron your costume, taking care to press your pleats and seams, and making sure all the wrinkles are gone. Once ironed, hang your costume up or fold it and put it away. When you bring it out to wear it again, give your costume a once over and see if it needs ironing. And since nearly every hotel now equips all their rooms with irons, there's really no excuse not to. Also, make sure you iron your garment on the appropriate setting. You don't want to scorch the fabric or melt it. Most irons have the settings written on them, so you can see exactly what setting you need for your costume. If you have no idea what fabric your costume is made of, start on the lowest setting (acetate/acrylic/silk) with no steam and slowly work your way up. When you notice the wrinkles gently coming out, keep the iron on that setting.
Wigs are probably the most annoying item to deal with in terms of maintenance. Unstyled wigs are easy to wash, using a little bit of shampoo and some warm water and left to air dry. And just a reminder, do not use a blow dryer on a wig - you might end up melting the wig fibers and ruining the wig! Let it air dry for a few hours and then brush using a wide-tooth comb or a wig brush until soft and smooth. Styled wigs are almost impossible to wash. If your wig has a stubbed pony tail, or braids, or crazy spikes and bangs, chances are you have to leave the wig alone. You can use some aerosol hair spray to control flyaways or re-fluff bangs, and trim some hair using tiny scissors, but other than that, you just have to be careful with the wig and keep it safe from damage.
3. Packing and At The Con
Just like at home, you want to make sure your costumes are contained and protected while on your way to and from the convention. Since you have everything organized, it's easy to take your garment bags and storage boxes with you in the car and to the hotel. When you arrive, either keep your costumes in their respective containers, or transfer them to the dressers and closets provided in the room. Just make sure to pack up everything before you leave in a neat fashion and getting home again should be no problem. Balling up your costume and throwing it into your suitcase isn't very helpful to keeping your costume intact, so take a minute to fold it up and place it in your suitcase. You will thank yourself later!
Another option, for those larger props or wigs that can't fit into a car or suitcase, is shipping the piece to the hotel where you are staying. Sometimes you can't fit wigs or swords or wings onto an airplane, so packing them up safely and securely in a large padded box with a very clear shipping address can save you a lot of grief. Make sure you use UPS, or another shipping service that offers online tracking, so you can track your package and make sure it arrives at its destination. Nothing is worse than arriving at the hotel only to find that your prop got dropped off in the wrong city or at the wrong hotel. Make sure you use plenty of bubble wrap, plastic air bags, plastic peanuts, paper or foam to secure the inside of the box to prevent any damage to your prop while in transit. You don't want anything breaking inside of that box! Try to ship your prop and time it to where it arrives around the same time that you do, or make arrangements with the hotel for them to hold the package until you arrive. While it can be a little pricey, shipping your larger costume items will definitely help when you just can't take it with you.
Credits: Lily Cosplay; "Costume Care" [online] available at firelilycosplay.com