Set And Setting is a term used to refer to the way a person feels and the environment a person is in, when consuming drugs. It can not be understated how important set and setting is.
Set is your attitude. Setting is your physical surroundings. By making sure your mind is ready and the environment is right, you will minimize the chances of a negative drug experience.
Set: Before consumption of any drug, you should prepare your mind. Do a little online research and find out what effects a substance has on the people that consume it. Erowid experience vaults lists various drugs and the personal experiences of people who have used them.
When working with a drug that is considered psychedelic, mind expanding, or hallucinogenic, it is best to have a purpose in mind prior to ingestion. A spiritual, medical, intellectual, or psychological pursuit will give the experience meaning.
Treating any drug with mind expanding properties as a recreational thing (to be done for fun) is a bad idea, negative experiences are common with this attitude.
Approach the consumption of such items as sacred. Altered states of mind can aid in healing and understanding the universe, yourself, and those around you.
The way you feel when you take these substances is usually amplified. If you feel depressed or angry just before you take them, you will probably feel more depressed or angry after you consume them.
Setting: The area where you plan on being while using a drug is also an important consideration. You should choose a place where you feel safe and where there will be few (if any) unexpected interruptions.
Only allow people that are trustworthy to participate. One person can ruin everyone's journey, pick your traveling companions properly.
An unfamiliar place with people you don't know may cause you to worry so much about external events that you won't be able to focus your mind, this can lead to a negative experience.
Sitter: A sitter is a person who looks after a situation in which others are consuming drugs. The sitter does not consume the drug(s) that other participants are using.
Instead the sitter monitors the situation to make sure that no one gets hurt. Not all drugs require a sitter but it is recommended that you have a sitter present anytime you first try a drug.