1) Over priming your engine.

When you over prime the engine, it can cause excess fuel to be splashed and drawn into either the exhaust manifold or the intake manifold. If the fuel ignites in the intake manifold, it can cause an engine fire.

2) Base-to-final turn.

Your base-to-final turn is the point in the traffic pattern that has the greatest risk for inadvertent stall/spin. If you overshoot final and cross-control the plane, you're setting yourself up for problems.

3) Inadvertent flight into clouds at night.

Night flying has risks that revolve primarily around disorientation and illusions. Inadvertently flying into a cloud can be hazardous for both instrument-rated and non instrument-rated pilots.

4) Frost.

Frost is a danger that isn't always obvious. Even a thin layer of frost can destroy up to 30% of your lift.

5) Scud running.

If you're diving below weather to maintain visual contact with the ground, you're opening yourself up to a CFIT accident, or colliding with something sticking out of the ground.

6) Get-there-itis.

Pushing to complete a flight is one of the worst things you can do. It's better to be safe on the ground than sorry you're in the air.

7) Not doing weight and balance.

Even if you're familiar with your aircraft, regularly performing weight and balance is a good idea. Remember, your aircraft's maximum gross weight isn't a performance limitation, it's a structural limitation.