I feel like a lot more needs to be said here. I'll try to be brief, but Salvia is not for the faint of heart and can have serious long-term side effects, so it's better to make sources of info like this one more complete.
Absolute ground zero-th of all, you probably don't want to trip salvia. Even experienced drug heads don't do a lot of salvia. It's super-duper-de-dooper hardcore, even though it's somewhat safe and very short-term, relatively speaking. It's like smoking crack or something. Or taking heroin. You are in strange and somewhat f'ed-up company to do it, and you may be much better off in the world if you understand 'curiousity killed the cat', decide not to give yourself full-blown schizophrenia, and otherwise take a skip on the full depth of what it will be like when you die, as it makes living much more complicated to the point that you literally will wish you could go back and not do the salvia. Unless you've actually planned on going mildly insane and becoming a loner or a commune hippy or something, it's better to take a whole lot of other things than salvia. The main thing is, you've got a secret Jesus complex if you think this is a good idea, and you are wrong if you think the life of someone dealing with post-hardcore mild insanity is easy even to the point of being bearable.
In short, it's not 15 minutes, it's years of growth and recovery and an attempt to regain and reunderstand the relationship with reality you've taken for granted since childhood. If I had it all to do over again, and I wanted to be a positive and engaging social person with a strong personal warmth, I think I might skip salvia most of all.
Since I have done it, I've learned a role and a way of living that manages the intense insanity. It's not for everyone, but I can handle it. If you want to go on, you need to be prepared to have a lot of learning to do, and learn up front how to keep your trap shut. Not everything is best said out loud. Trust the remorseful and guilty.
Now, if you still want to know a few things about it:
First of all, never, ever trip salvia alone. At best you will be too paranoid of hurting your body to completely experience and let go of your body's safety needs, and you will not have a complete salvia hallucination. At worst, you will stand up in the middle of your trip and try to walk, and you will light yourself on fire, fall over a railing, walk into traffic, trip over something, etc. Always have a trustable hippy type there to be sure you are in good hands should you decide to maneuver around during your trip.
Second of all, don't be a spoilsport by trying to walk or otherwise

overreacting to the experience. As long as you followed rule one, you should be safe as long as you STAY DOWN and allow Salvia to take you for a ride. It's a 'party foul' to do it if you know you're in an unfamiliar setting, so no matter what you think seems smart while it's happening, take some old, old advice and stay on your butt and on your back until things settle down and you are sure you're not tripping anymore.
Third, if you do Salvia 'wrong' you may never get the peak experience. Plain leaf and tinctures and everything else is nice and a medicine for the ongoing insane person, but if you want to trip salvia like people mean, TRIP SALVIA, you need two things: extract-enhanced leaf, the strong kind, and a trip sitter. You also need a glass pipe, a bit of tobacco to plug the pipe, and a cigar lighter or something hotter, like a windproof lighter. The hotter the lighter, the more confident you can be that you are about to have the experience. You may also want to have something to calm your mind ready to smoke after the experience.
Apart from that, I don't want to spoil it for you. It's a wild ride, but ultimately an enlightening one.
Just don't do anything crazy - get a trip sitter.