Channel trailer:Your trailer should be short and sweet (around 30 to 60 seconds). Focus on showing visitors what your channel is about and what they can expect to see in your videos. Don't forget to encourage them to subscribe. Your trailer won’t be interrupted by ads, which will keep the user focused on why they should watch more videos from your brand.
If you are filming your video with a phone, be sure to turn it sideways and film in landscape mode. This will prevent awkward cropping or framing when you upload the video to YouTube, which natively supports the landscape format. No matter what you’re filming with, these tips can help your video to look professional and stay engaging for your viewers.
Time spent watching a video is part of YouTube's algorithm. So if your title, tags, description, thumbnail, or category are misleading, it's unlikely that someone who clicks on your video will watch it for very long—once they realize it's not what they were looking for. If people only watch your videos for a few seconds at a time, the algorithm will notice and will demote your video in results.
“A series playlist allows you to mark your playlist as an official set of videos that should be viewed together. Adding a video to a series playlists allows other videos in the playlist to be featured and recommended when someone is viewing a video in the series playlist. YouTube may use this information to modify how the videos are presented or discovered.”