maricybele, I've always been told the best time to gather is right before they bloom same as blackberrys. But i've been trying to decide to take a chance and try picking some now.

When i dry mine i put them in small brown paper bags and keep them on the frig till they're dry(its also fairly dark there) if i have a lot of different leaves to dry i keep them in my pantry till dry. Some people may rather use a dehydrator.
Good luck with your tea and hope you enjoy it.
vickie