1. Don't marry to your beliefs. This is always a delicate balancing act because we do have to have some belief to make a decision, we just don't know if it's a right.
2. Don't predict the future. Can be derived from #1 so I suppose redundant.
3. Bet on people instead of ideas. I think this is great advice for VCs but have been covered many times by pg.
4. Make friends/Surround yourself with smart people.: Not extremely practical unless you are a famous VC but even then not trivial.
It would have been great essay if pg shared some stories and shared non-trivial insights that makes us better at doing above. BTW, I did got tripped at this line:
Another trick I've found to protect myself against obsolete beliefs is to focus initially on people rather than ideas.
Ummm... what was the first trick?