Valuation
Is the share price trading below intrinsic value?
Can be measured using DCFs, NAV, Private Market Value, Liquidation Value
Is the P/E ratio below 10x (or the inverse of the long term corporate bond rate, whichever is less)?
Is the company profitable? Preferably it has increased earnings for the past 5 years.
Is the company paying dividends? Preferably the dividend has been increasing and has been paid for some time.
Long term debt and bank debt must be judiciously employed. There must be room to expand the debt position if required.
Business
Is this a business I understand? Will the business be around for 50-100 years?
Is the business drowning in cash?
Is the business prone to change? Preferably not betting on change.
Sectors to Generally Avoid
Retail, technology, airlines
What sectors are left?
Consumer staples, healthcare, financials, energy, materials, industrials
How resilient is the business?
Is the business a royalty on the growth of others, requiring little capital itself?
How much damage can competitors do to the business?
Miscellaneous
How much of the stock do insiders own?
Have insiders been buying or selling?
How much are insiders paid relative to their stock holdings?