Relations are great way to keep your sketches from becoming cluttered. If your design intent is to have every hole in your design the same size, you can set all of the holes equal to each other and dimension one hole, changing this dimension will change the size of all the holes. Relations can also be used to make alignments, make things tangent or concentric, and more. Below is a brief video showing some basic relations vs standard dimensions.
Configurations are great way to quickly compare multiple dimensions, hole patterns or design changes. They can also be used to make a family of models with varying dimensions. The video below shows a basic configuration.
For more information on any of these topics or suggestions for tips you would like to see here, please consult with the SME E-Board