Just remember, shipping spirits/alcohol without a licenses is illegal. That being said, (

) if it was up to me, I'd use UPS from a place I know wouldn't ask any questions.

Put labels on boxes designating something other than spirits/alcohol. I'd also use labels designating "Fragile Glass", and labels with arrows designating "This Side Up." I just happened to find a site you can print those very labels from.
http://www.samplewords.com/ Might have to search a bit.
FWIW, I work for a company where I'm sometimes required to ship packages out. I'm not bragging, (really I am) but I know how to pack things in order to minimize damage. I'd use extra cardboard or double wall boxes, cardboard separators, styrofoam, styrofoam peanuts, bubble wrap, foam pieces/foam wrap, etc... what ever you have, and what ever you think it takes. I's better to be safe than sorry. Also, U-Haul has styrofoam wine bottle shipping containers that might be of use to you. Like Brisko said, some of these ideas are from other sources.
Hope this helps. Good luck.