The thumb rule is whenever there is a CPT code on the UB form and its status indicator is S or T, then modifier 25 should be appended to E/M code.
Some of the common procedure that will require use of modifier 25 to the E/M code are:
Any CT, MRI, or Ultrasound,
Infusions or injections
So if you find any of these on your chart you can append modifier 25 to the E/M code