In plastic with an address (both to and return addresses) inside. I used to send UPS but found that the cost is higher and I don't like that they drop things on the front porch so often--even when I'm home. USPS--my postal clerks always weight and factor the destination and then advise whether the flat rate or first class priority is best--I always ask that it not be left on a front porch--if sending to some place like an apt I'll usually spring for a signed return receipt--it's only about 2-3bucks extra. That way it doesn't get left on the porch.

I mail quilts frequently and can safely say "don't bother insuring them". I have a friend who recently retired from the post office, and when she told me what I would have to go through getting re-embursed should one get lost I was appalled! She suggested wrapping in tissue paper or roll into an old pillow case, then buying the correct size box for "Priority Mail". The post person helped me select the correct size, it comes with a tracking no. and insurance and was guaranteed to arrive in three days (Nev. to Virginia). My friend received it as promised and it was very reasonable.

I have used UPS to send my quilts. The service is excellent. You can save a lot of money by finding out in advance how they charge. For example the first time I sent quilts I used a long, low box and found out that a square or cube would have been several dollars cheaper. The next time I shipped, I bought a box from the UPS store at a cost of $9. Now I know what shape I need and get my own box in that shape before I send.

I had an interesting thing happen to me last Christmas. I ordered a box of very expensive homemade candy. It arrived all wet with the box open- horrible.
I filed a claim online and got a check within a week. I was shocked as the USPS is usually very frustrating to work with. I sold on Ebay for years and can attest to USPS being a nightmare :)
Having said this- I don't insure either. But the seller of the candy insured it. Boy was I glad!
There is insurance included in Priority packages. It depends on the amount and size.

there are shipping comparison websites where you put in the to and from zipcodes, weight, and dimensions, and it will give you rates for the different carriers.

Putting the address of the recipient inside the box is an excellent idea!

I've mailed quilts all over the country and to Canada. I've always bagged them first in a blanket bag then placed in a carton the right size for the quilt. Taped very well. I always send priority mail with insurance and delivery confirmation. I do not put anywhere on the carton that it's a quilt. For international I put fabric on the custom slip. I've never had a problem with this method. About 10 years ago I had someone want me to use UPS instead of mail- they thought it would be a better way. It cost 3 times as much and took 2 1/2 months for the quilts to travel from Michigan to Texas. It was a nightmare! The tracking showed it sitting in Chicago for weeks. No one seemed to be able to figure out why. Never again. Since then I stick with the mail.

I send things to my daughters in the city. I don't send it to their home, I send it to their office and am sure they get it then. This way I don't have to worry about it being stolen off their porch.