There are a few ways to preview a video:
• Shift + space key. When a video is selected in the thumbnails view, press this key combination to preview the video inline. This is a quick way to peek at the video if you don't need to see all the details. It's also convenient if you want a small image even for HD videos.
• Space key. Preview in Quick Look. When a video is selected, press this key to open a new window. You can also play the video in fullscreen from here.
• Open for Editing. Choose "Open for Editing" from the File menu or double-click a selected video to open it in a new editing pane. You can press the play button to play a video, or drag in the timeline at the bottom of the window to select a smaller portion. When you press the play button and a selection is set, Clipstart will only play that selection.
When organizing your videos with tags, use the inline preview or Quick Look to watch a few seconds of the video, then tag appropriately and move on to the next one.
If you prefer the space key to use Quick Look, you can change this in the preferences window.