"I heard it's about to go up" is the single most common reason people buy their first stock, and it's also the least reliable one — it gives you no framework for what to do next, whether the stock rises, falls, or does nothing for a year. A short, honest pre-purchase checklist fixes this: what does the company actually do and how does it make money, has revenue and profit been growing over the last several years, who are its real competitors and how is it positioned against them, and what does the company itself list as its biggest risks.
That last one is easier to check than most people realize — every U.S. public company's 10-K annual report (filed with the SEC, freely available on EDGAR) includes a "risk factors" section where management discloses, in its own words, what it sees as the business's real vulnerabilities: competition, regulation, key customer or supplier concentration, and more.
Correct moves you up, wrong moves you down — reach 100 to master this lesson.