There are a few ways to preview a movie:
• Space key. When a movie is selected in the thumbnails view, press the space key to preview the movie inline. This is a quick way to peek at the movie if you don't need to see all the details. It's also convenient if you want a small image even for HD videos.
• ⌘Y. Preview in Quick Look. When a movie is selected, press this key combination to open a new window. You can also play the movie in fullscreen from here.
• Open for Editing. Choose "Open for Editing" from the File menu or double-click a selected movie to open it in a new editing pane. You can press the play button to play a movie, 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 movies with tags, use the inline preview or Quick Look to watch a few seconds of the movie, 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.