Here are a couple of pitfalls to avoid during Turbojet proving runs:

1. Not adhering to OpSPecs- Don't takeoff VFR in a turbojet without C077
2. Not weighing baggage- Have a "scale" handy at all times
3. Not following GOM and A008 during Divert / Changing destination (Operational Control).
4. Not treating the feds as passengers- Safety briefing/briefing cards
5. Not handling maintenance discrepancies correctly- Follow GOM and D095, especially when faced with an outstation maintenance issue. Anyone that touches the airplane must be on a drug program and must coordinate with the DOM.
Hope this helps!