While I have done well with individual stocks and thought I'd continue to buy and sell individual stocks well into retirement, a few years before retirement I realized doing so was too much like work.
Too much work, for sure.
Here's a brief overview of the bare minimum I'd do before investing in individual stocks (TL; DR version: It doesn't fit on an index card):
Learn the company
1) Read the last couple of 10-K reports, the most recent 10-Q report, and all investor material on the website
2) Listen to the the last couple investor calls
3) Put together a spreadsheet of quarterly financial data and ratios going back at least three years
4) Learn the company's products and their key markets
Learn the industry
1) Read competitor company reports and investor presentations
2) Seek out sector specific analysis and / or trade publications to understand primary sector drivers
3) Try to understand what happened to the market and it's company's during the last period of cyclical stress
4) Build a spreadsheet that calculates key financial ratios for the major players in the company's sector to use as a benchmark
Build a fair value pricing model
1) Either using a discounted cash flow projection or some form of relative value framework I'd want to have a way of calculating a price target or valuation metric that would generate buy / sell or rich / cheap signals
Monitor all of this forever
1) Update all of the above
2) Continue listening to quarterly conference calls and periodic investor presentations for both the company and it's key competitors.
3) Read 10-Ks and Qs as they become available
Build a diversified portfolio
1) Do all of the above for 19 or more additional companies.