Taking salvia concentrates for first timers is like learning to drive using a formula1 car
I had some very interesting and intense salvia trips, most were done with a 5x concentrate and chewing plain leaves. Smoked thru a disposable water pipe, straight no mixing, small doses(around 0.2g) of 5x concentrate seem to have enough powert to make you hallucinate

It never lasted more than 10 minutes total, the comedown was always euphoric and clean, like having a refreshing shower.
I usually did some drawings right after the trips, to better remember what happened, but I seems my memory was not affected and I still recall the feelings and visions of that times.
Mostly it began with a rush of heaviness thru the skull and limbs(like being squeezed, rubbed or tied strongly), followed by a tingling sensation on all the body parts. Once this ends, the relaxation kicks in. The first visual perception effect was seeing Earth's magnetic field and it tried to bend my body into its direction(horizontal S-N)...I remember laughing like mad coming out of the toilet where I smoked it, walking bent on one side under the effect of the visualised magnetic field

) Usually I made it to the couch(sometimes didn't, so the floor was there) where the really interesting things started to happen. I remember it always felt like perception of the world just cracked in my head and started to slowly but strongly unfold like a folding fan or a peacock's tail.
It was like each fold contained a whole new world or universe maybe, I only had to choose where to go...I usually ended in one with a happy farmer on a tractor and a nice lady working on a field. I remember his smile and positive vibe, I always wanted to stay with them, but he always let me know I had to remember my true place and if I wish, I can come visit again. As the effects started to fade, the folds kept closing back and sealing the initial crack from where it all began. At the end, there wasn't left any physical weight or fuzzyness or whatever...just a clean happy brain
Another time I used a stronger dose(0.3 - 0.4g of 5x conc.) and had the same onset, except that I chose to go in another fold and there was my body suspended in some kind of fractal web which was composed of copies of my body, like a foam of bodies stretching to infinity. Closest thing in reality is Alex Gray's art, I think the effect leaned towards the effect of DMT but way slower(judging from others descriptions).
Craziest experience ever

Totally introspective and trippy.
A friend of mine(I was sitting on his salvia trip) experienced almost the same effects but not pleasant, he didn't meet my "farmer friend", instead a giant clumsy smurf told him to stay under the carpet, "nothing for you here" he said. You can imagine my friend was quite scared after and probably never tried it again.
My conclusion - salvia is fantastic, probably the best/strong hallucinogenic drug besides DMT. I still have some and I'll definitely buy some more.
If you are an aspiring or seasoned psychonaut, you must try it! But be advised to start slowly(not 80x, wtf).
Happy trippin!
*the "salvinorin A" man

lots of knowledge on the site.
http://www.sagewisdom.org/
A must see video for salvia enthusiasts:
[video=youtube;0T_x__Xh4Ew]http://www.youtube.com/watch?v=0T_x__Xh4Ew[/video]