I saw an article by Barry Ritholtz about putting together a short list for common errors that investors make. Robert Seawright then expanded on it with 30 Investing Truisms. I love this sort of stuff.

Here are some for poker:

1. A check-raise on the turn or river from a passive player is a monster.
2. Don't pollute your HUD with slow converging stats. That's what your pop-up is for.
3. Don't slowplay on draw-heavy boards vs. multiple opponents.
4. A triple barrel bluff vs. a relative unknown is almost always spew.
5. You need to have a tilt-plan in place before starting a session. Otherwise, you are like an electrician trying to install a circuit-breaker during a thunderstorm.
6. BRM can extend or shorten your life - regardless of your skill level.
7. At the micros and low stakes, your best strategy for dealing with a aggressive 3-bettor who has direct position on you is to switch tables.
8. Losing with KK against AA consitently isn't always a "cooler" - it could be a leak.
9. Calling with low and mid suited connectors out of position vs. a three-bet with 100 BB stacks is burning money.
10. There is no "in a vacuum" - there are always reads you can make and those reads are important.
11. Balance is not only unnecessary but also leaves a lot of money at the table at the micro and low stakes.
12. In general, valuebets should be bigger and bluffs smaller since most people have fairly inelastic continuing ranges.

Please add some of your own!