Mobile Phones

If in doubt, turn it off.
If travelling to a sensitive location, in an urban area do not use your phone within two or three miles of the location, or in rural areas do not use it within ten or fifteen miles of the location. This will prevent the creation of a trail that associates you with that location on that day.
If the location you are going to is nowhere near a route you regularly travel, turn off your phone before you start your journey there.
However, do not always go to places far from your home. A truly random sequence will include clustering. If you are always going locations far from your home, they can be able to back track you to your home or office based on the locations you are avoiding.
If you desperately need to mask your location, let someone else carry your phone around for the day - but this is only realistic if you take all precautions to prevent generating other document trails whilst you are moving around.