If you've ever been in a workout class and felt lost as the instructor shouts, "Burpee! Plank! Kettlebell swing!"—we understand. While those moves may not look all that difficult, each requires a little extra attention and know-how. That's where we come in. Below are step-by-step guides on how to perform 9 classic exercises with perfect form, so you know where to feel it and what muscles you'll be strengthening.