We charge hourly and try to catch as much as possible, sometimes charge for parking (we should every time in DC). Charge travel if over 50 miles, rental of any test equipment as this equipment cost anywhere from 500.00-68,000.00 dollars plus yearly calibration fees, rental rates are from one time per job of 50.00 to 500.00. Minimum 3 hours 4 hours on emergencies.
Have seen 600 amp fused safety switch on a job ticket but no fuses, when questioned the electrician admitted he forgot to list the fuses. That can get costly, I know they miss many minor (and sometime major) parts.
I prefer to have most cost built in the hourly, we have been accused of having a high hourly fee, only to be told later the less expensive guy had a truck fee, tool fee, parking fee (even when the customer supplied parking) 15% misc. fee, hourly charge and 10 and 10 on top of everything, his rate was higher then ours and the customer was one upset puppy.