Stop defining the same CSS properties over and over again. Utility classes are at the heart of Expressive CSS. They are easy to write and understand. Using them reduces the necessity to re-declare the same sets of related properties over and over again, keeping your CSS lightweight, scalable and easy to understand.
Document your classes as you go. Use them as building blocks for your html template library. A great example is the Tachyons Component Library.
Maintain consistency by using utility classes for font size, weight and styling. Margin and padding are 0 for