Before I begin, I feel the need to mention that Salvia isn't legal in all 50 states... but as long as it hasn't been outlawed in your state yet, you should give it a try before it does become illegal.
Erowid Salvia Divinorum Vault : Legal Status <-- this should help.
A lot of people may already know about this, but I figured I'd share anyways.
What you'll need:
1) A bong
2) Butane "torch" lighter.
3) Salvia Divinorum - also known as Diviner's Sage, Maria Pastora, and Sage of the Seers.
The first part is easy enough to come by. If you're in desperate need, try
Water Bong (Make one yourself).

This is the kind of lighter you should be using. That particular model/style isn't nessicary, just that type of flame (to clear any confusion).
Salvia can usually be obtained at any local head shop but can also be ordered on the internet easily (Google is your friend).
Now that you've got everything together, the rest is pretty obvious. Pack the bong, light the salvia, and inhale. Hold the hit in for at least 10 seconds to get the full effect. BE SURE TO PUT DOWN WHATEVER YOU'RE SMOKING OUT OF QUICKLY! This is doubly so when smoking out of glass. Don't wanna go and break an expensive piece because you got too retarded to hold it.
If you're used to smoking marijuana, be prepared for something COMPLETELY different. You'll only need one hit for a good 2-5 min trip and the effects usually come on MUCH quicker than marijuana.
From experience, I can tell you theres no point in buying anything stronger than 21x extract, as it can not [repeat: CAN NOT] become any stronger than 21x. Also, I'd advice against buying un-extracted leaf. The leaf itself isn't potent enough to make the user 'trip', but by smoking around an ounce a nice 'buzz' can be acheived. Again, this is nothing like a marijuana 'buzz' so don't expect the same results. Another good tip is to have someone you trust with you and stay sober until you 'come back', kinda like a chapperone. 'Groovy', mellow tunes are also highly reccomended to keep the trip light and happy, while the television usually has the opposite effect due to commericals/etc.
It's worth mentioning that feelings of increased body temperature are completely normal, even to the point of sweating profusely, so keep some cold water handy. Also, a quick, cool shower is good to get yourself out of a bad trip in a hurry, but
have your chapperone help you so you don't hurt yourself trying to get there or slip once you're in there.
Hope you guys have fun with this, and remember: Salvia isn't going to be legal forever due to it's intense hallucinogenic nature so take advantage of it while you can!