Best practise in Embedded Programming (C/C++):Interrupt Service Routine - ISR

Thumb rule for ISR is : It should be short and sweet.
1) Will not have any parameters or return values.
2) Should avoid performance hit operations like floating point operations.
3) Should not contain non-entrant functions.
If somebody gives you an example code to identify the problems in the ISR routine, these points should be considered to identify the faults.