I make sure the clothing is steamed and looks as good as it did for the photos before I wrap it. I fold it and put it in white tissue paper, then in a waterproof tyvek bag that is the right size for the clothing. I include a business postcard, as well as a personally signed thank you and the packing slip. If I'm doing any shows in their area, I include a show card. The garment also has a hang tag with our web store links on it.
I seal every parcel, bag or box with heavy duty shipping tape, print out a label from Etsy, and I paste pretty stickers on the outside so the package looks special. I've gotten many comments on my packaging looking nice and being pleasant to open.
I don't understand sellers who toss a wrinkled garment in a bag with no tissue or anything to keep it from sliding around. And I think including the packing slip and a thank you is so important. It's a sign of professionalism and I think buyers appreciate it, and may need it, especially if they purchase a lot of things at once from different sellers.
Jen