After all, there will be dramatic twists and turns, which is why the “bet on the jockey, not the horse” mentality is so prevalent.  And yet, somehow, many angels don’t plan accordingly.

Mistake #11: Investing in one of the first deals they see – Some of the early stage investors invests in the first company they see. Excited about their new role they don’t do much research and study. Instead they must do thorough due diligence. Sometimes the companies they invest in are out of their domain completely. In their hurry to invest they even end up signing the company's documents without having a lawyer review them.

 Mistake #12: Not reserving additional capital for the follow-on round – Follow up rounds which are inevitable in startup world is sometimes forgotten by these investors. They don’t reserve additional capital for that.

Here is a definitive guide to Angel Investing from over 25 Angel Investors