San Pedro is the best drug known to man! I have made san pedro tea probably 10 to 15 times and almost every trip has been great; and those that were weak were because i screwed up the batch through my own impatience. If you want to make the tea just mix the cactus with equal parts water in a blender and pour it all into the biggest pot that you can find. I wouldnt use less than 18 inches, but the more the better really. Also you can cut out the core to cut down on volume because it contains no active alkaloids.
After you have it all blended down set the stove to medium low and bring it to a boil. This alone will take 45 minutes, stir it the whole time continuously. Take it slow, be sure to have a whole day set aside for preparation where you can just sit around and smoke bowls and cook, I have ruined several batches trying to cram the whole process into my schedule. Let it boil for 4-6 hours, longer if you want. It will separate out into layers when it is ready so you will be able to tell. During this whole part you can increase the temperature slightly and you dont have to stir the whole time. Just make sure nothing is sticking to the bottom or it will start to burn. Also adding lime juice helps with the extracting of the mescaline from the pulp and it also makes it more palatable later on.
After the shit all serperates out, strain it through a cotton cloth and discard the pulp. If you have more liquid than you want to drink you can boil it down farther, but the more you do the stronger it will taste. This is one of the worst tasting things ever, but it kind of is an aquired taste, ive come to kind of like it, but drinking large quantities is still a pretty daunting task.
If you dont want to deal with the tea and have some basic knowledge of chemistry there is a relativly simple acid-base extraction that you can do. I dont want to explain it here but you can just google it or get it off of erowid. there are a few different meathods out there, but they all work about the same. Unless you have some equiptmet though you will only be able to extract the alkaloids, not pure mescaline, its about 50% pure. The downside is that you have to pay for some chemicals, xylene is like $20 for a small container and its just not enough. There might be a cheaper solvant you can use but i dont know of one.
Mescaline is probably my favorite psychedellic. It is so mellow that you can go introspective with it but if anything comes up you can still function perfectly well and it is kinda fun to go through normal tasks in a higher state of consiousness. My one and only word of advice, dont fry around drunks! or tweakers, the only potential way to have a bad experience is to have to sort out drama or violence. uhhhh.... enough said i think, if you read all of this Ill be very surprised, anyway enjoy!