Tailoring the U1 and U2 dials for instant switching between landscapes and action.

The official Nikon manual tells you what the buttons do; a "Mastering" guide tells you when, why, and how to use them. Whether you download a PDF or buy a physical copy, a great D7200 book focuses on:

The D7200 is highly customizable. A good guide will walk you through the "Playback," "Shooting," and "Custom Setting" menus.

Why shooting 14-bit Lossless Compressed RAW is essential for post-processing.