Perhaps a simple check list for a rough running engine along the lines of:
- Mags on both
- Fuel pump on
- Fuel quantity (change tank)
- Carb heat hot or select alternate air
- Oil pressure / Oil temperature check, if low pressure / hot then shut down.
- Vibration - if high shut down (before you cant see instruments
- Visible oil - if its obscurring the wind screen shut down before you cant see
- Fire - shut down, enter engine fire drills.
ABOVE ALL - concentrate on flying the aircraft rather than diagnosing the problem, don't be distracted from flying the aircraft