Use the lowest possible supply voltage, try reducing the clock speed while still performing the work as fast as possible. Disable clocking and cut supply voltage in as many areas as possible. Avoid integer divisions on ARM Cortex M0. Use a device with only the needed amount of peripherals, with just enough RAM and FLASH to perform the required work.
MICROCONTROLLERS
Everything microcontrollers: projects, questions, new releases, etc.
dragontamer's Beginner Guides:
Beginner Series I: What is a Microcontroller?
Beginner Series II: The "Generic" Microcontroller
Beginner Sidenote: Microchip's Signal Chain Design Guide
Beginner Series III: Skills and Complexity Tiers
Beginner Series IV: Deep Dive into Microchip's AVR EA
Soooo....basics, amiright?
It's nice to enumerate it. I'm sure a lot of people don't think about their microcontroller is having parts that can quiesce. Reducing the frequency of your clock until it meets your needs just barely, that's something probably most people don't do
Interesting, never really occurred to me that flash could actually be holding the processor back like that.
I wish I knew where/how this person found all the flags to play with for power.