The Budget Constraint: Budget constraints are often easier for students to understand than preferences or utility.  Students are usually fairly quick to grasp how changes in prices and/or income change the shape of the budget constraint, so a few simple examples are usually sufficient.

 

A quick reminder of how the budget constraint divides the space into affordable and unaffordable regions is helpful.  In some cases, reminding students that this is similar to what they may have seen as a production possibilities frontier in the past can help them see the budget constraint as essentially defining a consumption possibilities frontier or set.