Ready for the long answer?
Typically, my clients use USPS services. Much of how you need to pack your items depends on how fragile they are. My client Pam, who ships jewelry to me from Craft Gal Creations in Chicago was nice enough to allow me some extra time with her products so I could put a small "how to" together for the more fragile items for you! (Thanks Pam! Everyone should check out her shop!)
Pam makes wonderful natural stone jewelry, along with some very fragile glass and beaded items.
She takes the time to pack her box with padding on all sides, extra tissue, or bubbles depending on what she has on hand.
The boxes help separate items - and the inside packing helps to keep them from breaking on the box. It also allows Pam to send me extra notes, or special requests on a items.
Obviously, not all items need to be sent with such care. T-shirts, hair bows, and other soft items such as crochet and knit items can simply be put into the box. I do always suggest that you inclose a packing list so I can verify how many items arrived from you.
I hope this serves as a nice quick reference guide for packing. If you don't already, I would like to encourage you to check out some green options for packing supplies. Re-using boxes, and other supplies! It's just the right thing to do!