Here is a link to a wonderful discourse on Deborah Secor's web site on the best ways to mat, frame, store and ship pastels.
There are also a lot of great conversations on the Wet Canvas web site regarding these matters.
Some points to keep in mind
Matting
1. Always use conservation quality materials. Otherwise your mat and possibly your artwork could turn yellow and/or fragile with time.
2. One of the most suggested ways to mat a pastel is with a spacer. This can be either a purchased item manufactured specifically for this purpose. Or you can use scrap matboard attached directly to the mat. The purpose of this spacer is to create a gap for spare pastel dust to fall into, so that it is not immediately visible to the viewer's eye.
3. Mats should be neutral to the color of the painting. You want you mat color to enhance the painting, not to detract from it. Bright colors are usually very distracting, as can be a blinding white mat. The color often used is an off-white which "matches" the painting itself. The frame and the mat should never be the same width. The mat is most often the widest item, but this should be at the discretion of the artist. A reverse bevel can be used in the mat to help control the visibility of the pastel dust. Double and triple mats can help to enhance the look of the matting.
Framing
1. Your frame should enhance your painting, not detract from it. A frame that is overly ornate can overpower your painting and cause the viewer's eye to go to it, rather than the artwork.
2. Make sure the size of your frame is adequate to the size of your artwork. The rabbit (the space where the painting, glass, etc sit on the back of the frame) needs to be deep enough to accommodate the art, mat, glazing and spacers with enough room for points or nails to hold everything in place.
3. One great idea is to install turn-buttons on the back of your frames. This gives you the option to change the frame easily if your piece isn't selling, or if you just want to give something else a try.
4. Your frame color shouldn't compete with your painting. Colors often used are gold, silver, natural woods or neutral colors. The frame shouldn't be lighter than the lightest light in the artwork, nor darker than the darkest dark.
Glazing
1. You need to be careful in your selection of glass for your frame. The standard non-glare glass is often not used because it dulls the details in your work and fades the colors. A preferable alternative is a non-reflective optical coating, which is more expensive, but it presents your painting in a truer form.
2. Some people recommend against plexi-glass because the static can attract the pastel dust particles. But, plexi is a much lighter alternative than standard glass and there is no danger when shipping artwork of damage from broken glass. If you choose to use plexi-glass as an alternative, choose one that is manufactured strictly for the purpose of framing artwork. Make sure you treat it with plastic cleaner that is designed for this purpose. It will help to reduce the static electricity.
Storing
Here is a link to a great discussion in Wet Canvas about how to store pastel paintings. As with most topics of discussion, there are a great many opinions, and plenty that contradict each other. Storage matters can depend a lot on where you live. Some of the common methods include:
1. Get a large pad of tracing paper and keep each painting in a separate page. Make sure the pad is secured with something such as rubber bands so the paintings do not fall out.
2. Put them into clear bags (this is an archival brand of starage bag) and stack. Please note that some instructors recommend against doing it this way.
3. Cover with glassine and hang from skirt hangers.
4. Mount on foamcore, cover with glassine and stack.
5. Mount and mat as you would normally and then cover with glassine and stack.
6. Mount, mat and glaze normally and then tape the whole package together.
Shipping
There are containers made with the express purpose of shipping artwork. One of the better known manufacturers is Airfloat Strongboxes. Plexiglass is often preferred to regular glass when shipping. One other thing to keep in mind is insurance. You'll need to be able to prove the value of your work with a prior bill of sale or something similar if you need to make a claim. So plan accordingly when filling out the insurance paperwork.