1. I picked a simple but useful function and explained it on a white board. Obviously the interviewers knows what your function does so its a great opportunity to show working Excel knowledge and your ability to communicate technical concepts to others 2. Consider it might not have to be math/finance/econ based. I think I picked something I learned in anthropology. Pick something meaningful to you and that you know well so you can explain it well. 3. Have 2-3 examples for each behavioral that you expect, even better if they stem from your resume. Practice them! 4. Lots of resources on here for Gross Margin and other simple calculations they will ask like how does depreciation flow through the financial statements, ect. Study a little beforehand, I had no accounting experience and did fine because I studied. 5. They want to see your thought process, always a good idea to stay structured in your process and use a white board or paper if you need a visual, I did. Ask clarifying questions to get your assumptions.