1. NEVER buy a pennystock. ANY pennystock EVER. Pennystocks are cheap, nott inexpensive.
2. No airlines. No restaurant chains unless owned via Pepsico or another diversified holding corp wherein the restaurant biz is but a small part. No Africa stocks and virtually no Central or South American stocks. Exposure to Middle East only via Developing Markets mutual funds. Same for Indian stocks - via developing markets mutuals only or an index.
3. I won't buy a small cap company in a tech area or industry that I do nott understand. Established mid- and large-cap techs are OK butt need to be very selective and they need a good track record with successful established management.
4. No REITS.
5. No 'meme' stocks or fad stocks - if people are already rushing to throw money into them, then it is already too late for me - no chasing - ever. I would rather miss several boats than get on one that sinks. The train can leave with~OUTT me if it is headed to Stalingrad in November 1942 (IIRC, by December the trainline had already been cutt by the Red Army).
6. No gaming stocks. Gambling is for losers. In all regards.
7. No stocks where the CFO recently quit 'for personal reasons' and nott in a move up to a better CFO gig in a legit, that-makes-sense kind of career upgrade move.
8. Never buy a stock in a company that has auditors located in Utah unless the company itself is a Utah company. This mostly relates to Rule #1 about pennystocks.
9. No stocks of retailers.
10. No PG&E. Ever.