The basics of any investment starts with financial education. One must be financially literate to embark on any business venture. This is the minimum entry requirement even before we begin to talk about the other key principles that have already been mentioned, like risk awareness, diversification, patience, strategic withdrawal, and others.
Yes, to me in this thread, or rather in the OP I would have missed some more of the basics, like having an emergency fund. Some people jump into investing as if they are going to get rich quick without having the basic knowledge of personal finance. Any knowledge after them welcome. But if you don't follow some basic rules, they can give you all the advice they want, you are not going to succeed.