First of all, you need an idea for a drug. This can come from any number of places: a molecule in a plant; a receptor in the body that you think you can build a molecule to interface with; an old drug that you’ve tinkered with; and so on. This part of the story is extremely interesting, and I recommend doing a degree in it. When you think you have a molecule that might be a runner, you test it in animals, to see if it works for whatever you think it should do (and to see if it kills them, of course).
