What is your framework for doing your research/due diligence on an investment?

Been casually investing for a while (snp, bit of gold, etc) but want to get deeper into picking individual stocks. After getting an idea for a stock pick, what are peoples tried and tested methods for ensuring adequate research and due diligence? Is there any kind of checklist that has served you well? I.e meeting certain earnings requirements, certain details in annual reports etc. I appreciate this could be a “how long is a piece of string” question. But wanted to ask if anyone had any tried a