Salvia Divinorum (Diviner's Sage) is an herb of the Lamiaceae (mint) family. It is an atypical psychedelic that also exhibits extreme dissociative properties in high doses. The active psychoactives of the plant are Salvinorin A and to a lesser extent 2-Ethoxymethyl Salvinorin B. Both are opioid receptor agonists ( e.g. kappa-opioid agonist ). Salvia is sold as raw foliage, extracts, and tinctures. Never buy salvia as a joint or a blunt: salvia does not work when smoked this way. Salvinorin A is soluble in ethanol and acetone and both are used in the manufacturing of extracts. Extracts can range up to 80x, meaning that it is roughly 80 times as powerful as raw leaf per mass. Salvia is notorious for being one of the most intimidating psychedelics available. The compounds in salvia are the most potent naturally occurring psychoactives known to man. While salvia is legal in most countries, it is illegal in Australia, Italy, Spain, Sweden, and others; it is uncontrolled in the US, but illegal in 10states (Ohio, Florida, Louisiana, Oklahoma, Kansas, Missouri, Tennessee, Delaware, North Dakota, and Illinois), and bans are being considered in others. Wikipedia has a frequently-updated page on the worldwide legal status of salvia.
Salvia Divinorum has been used for centuries by the Mazatec shamans of central Mexico for the purpose of divination. It was also used medically by them to treat diarrhea, anemia, headaches, and rheumatism.
Salvia may either be smoked or used sublingually. Salvinorin A is not very water soluble. Salvia will not work if eaten, snorted, or used as a tea. It is debatable if salvia can be administered rectally.
Smoking is the most popular way to use salvia. Both raw foliage and extracts can be smoked. A normal lighter and pipe work fine. Torch lighters may be used for greater efficiency, and water pipes may be used to ease the harshness of the smoke. Because of the tremendous effects of smoking salvia it is highly recommended to be around a sitter if this is your first time. To smoke salvia, the flame on the leaves or extract for the duration of the pull. This is why joints do not work. The salvia must burn, it will not smolder. Inhale as much smoke as you possibly can; it is good practice to load one hit in one bowl and cache it. Hold the smoke for around 10 to 20 seconds. Exhale and then inhale more smoke if some remains. Repeat until you reach your desired state. Effects begin immediately after exhalation, peak for around a minute or two, and taper down for around 10 minutes.
Salvia may also be used sublingually, this is known as the quid method. This was the preferred method of Terence McKenna. It is not necessary to rehydrate the leaves, and doing so will actually remove salvinorin from the surface of the leaves. To use salvia this way, grab a handful (seriously, a big wad) of salvia leaves and place them under your tongue. Leave them there and chew occasionally. Effects will begin after about 15 minutes. Redose until you are satisfied. To end the trip you can spit out or swallow your salvia leaves. Effects can last up to 90 minutes. It is not recommended that you use salvia fortified leaf extracts sublingually. While it will theoretically be absorbed this way, it is extremely uneconomical and inefficient.
Tinctures are used sublingually. Be aware that they may burn a bit.
Salvia tea is one of the traditional ways Mazatec shamans used salvia divinorum. This method, however, is extremely inefficient because salvinorin A is destroyed once it is swallowed. Most likely salvia will only work this way if some of it is absorbed by the tongue as the liquid passes through the mouth.
Salvia divinorum may produce audio and visual hallucinations, sharpen the edges around objects, exaggerate or otherwise distort distances, cause complete ego death, an altered identity, severe confusion, feelings of becoming attached to walls or morphing into some other object, perceptions of other dimensions, and extreme dream-like states. An interesting property of Salvia is that in many cases, the sensory hallucinations experienced by users cannot be described or recanted after coming down. Users report experiencing multiple "other dimensions" or reality "fragmenting" around them. Visual hallucinations are are very common while using Salvia, and sensory alterations abound. Hallucinations caused by salvia are unlike most psychedelic hallucinations and are usually characterized by extreme zooming into an object, changed and often cartoonish tints, and objects morphing. If used in a high enough dose salvia can completely overwhelm a user's visual spectrum. Besides hallucinations, salvia changes the perception of objects. For example, you may look at a box but it might be interpreted as a human being, even if the box is visually unaltered. The dissociation caused by salvia will often cause you to forget your identity, where you are, who your friends and family are, and that you have taken a drug. Because of these effects, many people find salvia much more unsettling than typical psychedelics like LSD and mescaline.
Salvinorin A is a κ-opioid receptor agonist. Receptors are enzymes; they take one chemical and process it into another chemical. There are two major opioid receptors, µ and κ. Opioid receptors deal mainly with analgesia, µ-receptors create an addiction to the chemical, and κ-receptors do not. An agonist is something that increases the rate of action of an enzyme (an antagonist would decrease the rate of action). The κ-opioid receptor metabolizes cAMP (cyclic adrenosine monophosphates). These monophosphates are essentially envelopes that contain messages sent between neurons. Salvinorin A increases the metabolization of cAMP. With less cAMP, neurons don't talk the way they normally do, thus the dissociative effect of Salvia. These monophosphates are replenished in the course of three days.
Safety is very important when using a drug as strong as salvia. When smoking salvia, always make sure that you have a sitter if you are unfamiliar with the drug. Remove all weapons and sharp objects from your vicinity. Lay completely down and away from sharp drops. When smoking, make sure that your pipe is over a safe place and will not break or set fire to anything if dropped. It is not uncommon to forget that you are holding a pipe when the salvia hits so it is imperative to do this before ever inhaling. Make sure that your sitter takes the pipe from you when you begin to trip. Attempting to walk when high will either be impossible or unsafe. While it's virtually impossible to overdose on Salvia, it is possible to take too much. If you take too much, you'll freak out, and not even remember the trip. Thus, heroic doses are not recommended. If too much Salvia is ingested too quickly (i.e. more than three trips in a day), you cannot replenish your cAMP as quickly as you are metabolizing it. This will result in a cAMP deficiency, and you will feel the dissociative come-down effects of Salvia until your cAMP is replenished three days later.
 Having a good trip
Salvia can produce incredibly intense trips that can be as intense as breakthrough DMT experiences. These trips and even lighter trips however tend to freak people out much more as they often forget that they've even taken any drugs at all. Below is a handy guide written by a fellow /psy/chonaut.
I've written this guide to help others protect themselves against the possible negative sensations that may occur during the come-up on Salvia, and therefore maximize the potential for a positive experience. I've had many positive and negative experiences over the past couple years, and I hope my insight will help others to discover the enlightening and rewarding aspects of salvia for themselves.
1) Environment: I realize most people here understand the idea of "set and setting" however this can't be stressed enough when dealing with Salvia. One of the more common sensations during the come-up is becoming "one with your environment". People who are not experienced with Salvia usually misinterpret this to simply mean that you may feel as though you "are" the bed you're sitting on rather than your body etc, however this sensation is but one of many environmental sensations that may occur on Salvia. More often people find that they identify themselves as being one with whatever is stimulating them visually (with eyes open or closed), and therefore any visual cues in the environment that one wishes they could ignore will inevitably become an extremely relevant part of the trip. On a drug like LSD, a person is usually aware that they took a drug and can simply move to a new location if they are feeling bad. This is NOT usually the case during a Salvia trip, so it's EXTREMELY important to prepare yourself for the intensity of the experience by minimizing environmental stimuli as much as possible. In my person opinion, I'd recommend having no music, no lights, and no speech in the room. Letting go of your normal perception of the world is much easier when there is less external stimuli to distract and/or confuse you. Prepare for a trip into your very being.
2) Intention: Many people go into the Salvia experience with the intention of experiencing a thrill, like a roller coaster within the mind. I'd highly recommend staying away from Salvia completely if this is your mentality. I've found that there is only one kind of person who can actually enjoy Salvia, and those are people who desire knowledge pertaining to how consciousness works and what remains of ones being when the ego is broken down completely. Salvia is not fun, and it's not going to be something you can laugh about with your friends later on like alcohol, weed or even other psychedelics like LSD (not that LSD isn't an incredible tool for exploring consciousness). If you're the kind of person who desires this knowledge, simply focus on this intention while you hit the bowl. This will help you let go, and give you the ability to break through into a positive experience.
3) Don't fight it: If something goes wrong and you find yourself entering a trip while in a bad state of mind, the best thing you can do is GIVE IN. You've already taken the hit, it's too late to go back. Unlike other psychedelics you're probably not going to be able to understand the concept of "I took a drug" in a way that will be much help to you while tripping, therefore you must prepare yourself beforehand as it may seem impossible to prevent yourself from freaking out when the trip starts. I know this sounds scary, and that's because it truly is. YOU CAN PREVENT THIS however by following what I said about focusing on your intention and making sure you're completely comfortable with your environment. There many may come a time when Salvia simply catches you off-guard and you're going to be put into a position to act fast to prevent yourself from freaking out. If this occurs you MUST surrender to the trip in order to have a good experience, even if it seems like the Salvia is taking you someplace that is unbelievably frightening. If you try to hold onto your normal perception of reality when this occurs, it's pretty much guaranteed that you're going to have a bad experience you'll likely regret having. If you can get yourself to let go and simply flow with what Salvia is doing, you will likely have an experience that is truly wonderful and enlightening. I hope this advice will help others have a good experience, and/or help others realize whether or not Salvia is a psychedelic for them to explore on their personal journeys through life.
Salvia can be combined with a number of other drugs. Alcohol may intensify the effects. Marijuana intensifies salvia's visual effects, but greatly lessens the dissociative qualities. Opioids have been used in conjunction with salvia in order to make the trip less intimidating and more mellow. Salvia can also potentiate shrooms to a good degree and add a dissociative dimension to the trip. A salvia and DXM combination has been reported to produce quite an odd and enjoyable synergy. Salvia may also be mixed with LSA, creating very weird and powerful dissociative qualities not found in either drug alone.