How you hook viewers is very important. It increases Youtube view time because your viewers will watch the video until the end to see how the hook at the beginning “hooked” them. If a video features a project of any kind, show the end result first. A great result makes people more interested to see how you achieved it. This approach is great for all videos on Youtube. For instance, id you are shooting a fishing video show the catch first and your viewers will stay around to see it and will likely subscribe.
Another tactic is to start your video with a story about your video if it makes sense. Just make sure it is on topic and relates to your video.