The biggest mistake I see new investors make is that they don't do enough research. Researching a company or buying one stock is an enormous commitment, and it's important to understand everything you can about the company, its history, and future prospects before committing yourself.
You should look at their financials and ask yourself some questions about them—how much revenue do they make? How much profit do they make? What are their competitors doing? Are there any new technologies that could disrupt the industry in which they operate? Do they own any patents or trademarks that will help protect them from the competition?
If you don't know the answer to these questions, then you're not ready to invest in this company. You need to learn as much as possible about what you're investing in before risking your money.