What are some adaptations and tips for living with low income?

I ask this because a lot of advice about personal budgeting presupposes the reader has high means, such as the piece of advice “Make sure your rent is no more than 30% of your income,” when that is infeasible for Americans making minimum wage (or the infamous “just borrow a few thousand $ from your parents”).

What kinds of adaptations have you learned on low income? What strategies does one use when financial security is not a given?