What are some checks you make before investing in a stock

Hello, I'm really new to investing and ive been researching a lot. I've found some videos that were really helpful in terms of “checks to do” before buying stock in a company. I'm hardly someone who knows a lot of finance so i like the idea of having some rules of thumb to go by.

Currently I have 4 checks:

1. If P/E > 30 then it might be overvalued

Go to yahoo statistics -> search for company -> financials:
2. On the Balance Sheet, check that totalCurrentAssets/totalCurrentLiabilities > 1

1. On the income statement sheet, check that (Operating Income / Total Revenue) * 100 > 15

2. On the cashflow sheet : check that free cashflow is increasing each year / staying steady

While the guy in the video who explained why these checks are done made complete sense to me, as I said before, its not like i have the expertise to argue with it. Im curious about your opinions. Do these look like good rules of thumb? And if you have any others, please do let me know 🙂