In my Shopping class, I teach people how to right click an avatar's attachments and use Object Profile (or Inspect, in the Firestorm viewer) to find out what that great outfit is that someone else is wearing.
But with Mesh clothing and attachments, there's often a problem with that. Rigged mesh, especially, can be difficult or sometimes even impossible to select.
Just today, one of my students gave me a link to the estimable Strawberry Singh's blog, where she, Strawberry, reviewed a freebie item, a HUD called "What is She Wearing!?!?" It easily lets you inspect your own clothing attachments and those of avatars near you...and it's FREE!
Find it here: https://marketplace.secondlife.com/p/MB-What-is-She-Wearing/9129140?id=9129140&slug=MB-What-is-She-Wearing
Happy outfit snooping, and happy shopping!