How do you make an invisibility potion?

Any poison will do, when you have turned to dust you will be truly invisible. Joking aside, a potion to make you invisible does not exist. However, there are other ways to become invisible.

Aleister Crowley (a famous occultist) once boasted that he was able to make himself invisible after having shot a man (he was being robbed). The way he put it was that he wasn't truly invisible, but was able to walk through the crowd unnoticed.

There is a similar story in The Bible where Jesus was able to avoid an angry mob by walking through them unnoticed.

One magickal way to go unnoticed (and thus be invisible) is to take on the character of another. Want to go unnoticed in a crowd? Change your aura to be just like the crowd. Or take on the aura of someone completely different than you when you do not want to be spotted. Many will glance over you, thinking you are somebody else. Costumes help.