1. Even or though doing a thorough preflight, before getting into the aircraft, have one final walk around to check things like Oil caps, Fuel caps and jackets /clothing left on the tailplane... The fuel cap one bit me when I was very inexperienced, landed after noticing the gauges were a showing less than what I thought should be there. Realised my mistake of leaving a cap off, now a final walk around is an SOP, even if I need a ladder to see the caps on the larger machines.
2. Nothing ever needs to be done in a hurry in an aeroplane. When being taught to shoot accurately I was told "Slow is smooth, smooth is fast", same applies.
3.. I don't know even a thousandth of what I should know, and I am learning everyday. The bag of luck still has some in it (I hope).