What strength of extract did you get?
I agree with Justin, get a nice bong and some cold water.
I differ in that if its your first time with salvia I dont recommend you rip on it too hard, salvia + torch lighter = very hot smoke.
Give it a light rip, hold it for about 15 seconds, if you feel alert still take another and immediately put the pipe down, lay back and enjoy.
Depending on your tollerance at the 45 second mark when your exhaling the 2nd hit you can expect it to take over and whisk you away to salvia land.
During your trip you can expect to be unaware that your tripping. If your alone and its a good trip its absolutely excellent. If someone's with you, besides keeping you from hurting yourself, dont expect them to be able to do anything about a bad trip. As long as your in a good place mentally before the trip you wont have a bad time.
This is just my theory about sally...
If your the kind of person who's fight or flight mechanism leads them to quick reactions, and what I mean by that is you know instantly and act fast if your in danger, you will problably want a sitter just in case. My reasoning about this is if your tollerance is low or you get a real good dose, you wont know you smoked it and if something scares you, you might beat up your TV or sprint into a wall.
On the other hand, flawed as I am, instead of fight or flight I tend to get paralyzed when I'm scared so although that makes me something of a darwin reject, it works to my advantage when I'm not in control of my actions. Just something to think about.