For stand alone properties, I charge for the length of time from arriving to packing up and driving away - my hourly rate or proportion thereof.
If you are not already, then time yourself on a varied selection of your regular round, it will help get you rehearsed in what to charge, helping you to price more accurately and not underestimate how long things will take.
Whilst I agree that time is money, taking the time to listen to your customers, chat with them and establish a working relationship is to your benefit and is looking after your interests, I dont charge for this.
