Organisation is the key along with streamlining and standardisation of the mundane.
Have a calendar and make sure EVERYTHING is put on it, i.e. renewal dates for utilities/phone contracts, car service/mot/road tax, school holidays, school events, appointments, etc etc and keep it up to date.
Pay bills and answer correspondence etc as soon as it arrives - adopt a "just do it" strategy so you don't miss deadlines and don't waste time (and mindspace) worrying about things, trying to find things, etc.
Create pre-populated shopping lists on, say, Word or Excel and just print them out or have similar on your phone. Delete the stuff you don't need and that leaves all the stuff you do need and buy regularly - far quicker to knock things off a standardised list than start a new shopping list from scratch every week.
Meal planning - keep to the same rough pattern, i.e. a fish dish on Friday, meat and two veg on a Sunday, etc etc., so that you can plan your buying of fruit, veg, fresh meat and other perishables to avoid waste and to avoid having to do "mini shops" to buy things you've forgotten or run out of (which wastes time).
Plan your trips out, incorporate a shopping trip on the way back from picking up the kids from a party, school or activity - saves all that wasted time of coming in and going out multiple times.