This information is all already out there, but I thought a concise guide to propagating S. divinorum might be of interest.
Here are the mother plants:
Take a cutting about this big. Cut right below a node.
Trim off most of the leaves. Just leave a few at the top, and if they're big cut them down as pictured.
Place the cutting in a jar of distilled, filtered or spring water (I use a reverse osmosis filter). Put the cutting under bright light (direct sunlight is too much though). A humidity dome is not necessary or beneficial, in my experience, as long as you trim the leaves. 75F is a good temperature.
You should see roots forming from the lower nodes within a week or two.
Once you have roots 1/2" or so in length pot the cutting up. Don't let the soil dry out too much while the cutting is establishing. Within a week or two it should start leafing out and growing again. If the cutting looks sad don't give up! As long as the stem isn't completely squishy there's still a good chance it'll come back.
For my soil mix I use
1 part compost or worm poop
1 part coconut coir or pine fines
1/2 part perlite.
I top dress with compost or worm poop now and then and don't otherwise fertilize. If grown indoors a bright window or grow light is necessary; if grown outdoors light shade is best. S. divinorum doesn't like to be moved or overwatered, so don't mess with it more than necessary. This plant will do best in fairly large pots for its size; it doesn't like having its roots restricted. Salvia divinorum is a relatively easy plant to grow if you don't try to do too much to it.
You can take the leaves you trimmed from your cutting as a quid. I like 8 or so large leaves; you may need more or less. Roll them up and chew slowly without swallowing the juices until you're as far as you want to go. A dark, silent room is best.
Hope this is helpful to someone!