Hey,
My Salvia plants are growing like crazy at the moment. When I take a cutting, a cut it off, put it in a little beer bottle with water in, and place a jar over this to keep up the humidity.
They RAPIDLY start rooting. After a few weeks, I plant these in some compost/perlite/verimculite, with the jar over the plant to keep up the humidity. The cutting starts rapidly growing...remember this is the only way Salvia reproduces in the wild - it is designed for it (viable seeds very rare indeed).
Then I grow them in a tub, out of direct sunlight, and the tub has a few little upturned lids with water in to keep up the humidity a little...I don't even spray them now. Don't be too fussy with them or use a humidity tent e.t.c., it is not necessary...Salvia divinorum is a tough and adaptable plant and doesn't need pampering...mine do loose a few leaves now and again though (they weren't impressed with the British winter - can't blame them).