Pivot Tables in MS Excel & Google Sheets

Pivot tables (and cross tabulation) in MS Excel are great for exploring and analyzing data, but a) people seemed to be scared of them and thus b) nobody uses them.

A great place to start is the nice tutorial Saving Time And Energy With Pivot Tables by Anne K. Emery (also available via Learn Excel: An In-Depth, Thorough Tutorial (With GIFs) in the Intermediate and Advanced Techniques section).

Also great: How to get data in the right format with pivot tables. This tutorial shows you how to use pivot tables to reformat tables from 'long' to 'wide' - see the animated GIF below.