When I lead my live, virtual TechSmith Camtasia classes, previewing and editing are one of the most important skills that I teach. And a recent update to Camtasia makes previewing a lot faster.
Press the L key on your keyboard to move forward through a preview at normal (1x) speed when previewing. Press L again and you're at double playback speed. Press L a few more times, and you're at 4x speed up to a blazing-fast 8x speed.
Press the J key, and you'll go backward from 1x to 8x speed.
Press the K key to stop.
Check out a video demonstration by Andy at TechSmith here.