I'm learning about this myself, propagating native Calif. salvias. Here's what's worked so far.

My medium is perlite & vermiculite, mixed 1:1. I put it all in a plastic tray, the kind you germinate seeds in. The mix is wetted to feel damp, but not so wet as to leave any standing pool of water at the bottom of the tray. I've made that mistake ("Let's just add a little more water...") and had to discard a tray-full of mix. I use a dome to maintain humidity, but I also mist the plants from a spray bottle once or twice a day, as I remember to do it. Being without roots, they are at risk of wilting, which can happen quickly. My climate is dry most of the time, so YMMV. I'm using rooting hormone. I was using the Schultz stuff that Home Depot carries, but now I'm using Dip 'n' Grow, which seems to be more effective (but I haven't done a controlled test). My latest batch of Salvia clevelandii cuttings rooted in less than 13 days. That is, at the 13 day mark I checked them (scooped them out of the medium, one by one), and most had substantial roots (19 out of 24 cuttings), and the others may yet develop roots. My experience (admittedly brief) is that once you get over the hump of getting them to grow any roots at all, the roots grow very quickly. You can go from one little 1/2" root to a full "beard" of them in five days. I also use a propagation heating mat, but with warmer weather now, I could probably just unplug it. I have a lab type thermometer stuck in the propagation mix to monitor the temperature. The temp varies, but I try to keep it around 75F.