Want a highly optimized YouTube video? Read on…

You may put a lot of time into producing your YouTube video and be excited to publish them on YouTube. But don’t rush!
Spend the extra few minutes optimizing your videos, making it easier for users to find and share them. Otherwise some of your hard work and creativity could go to waste.

The YouTube video optimization checklist:

1. Choose a good video title — It all begins here. A good (accurate) title helps viewers know they’re in the right place, and a keyword-rich title is crucial for users to find your video when searching YouTube.
2. Upload a custom thumbnail — The thumbnail gives people a snapshot of your video. To hook viewers, upload a custom image that teases something exciting in the video. Your thumbnail image should have a 16:9 aspect ratio.
3. Insert YouTube cards — Add some interactivity to your video when it’s viewed on most desktop, Android, and iOS devices. You can use cards to link viewers to a specific URL, point them to another video or playlist, ask them to subscribe, and more.
4. List relevant tags — Enter any keywords that are associated with your video content, location, subject
   matter, or featured artist. Good tags can boost your ranking in YouTube search results. Stumped for how
   to tag your video? Try searching for similar content on YouTube and see what they auto-suggest.
5. Write a good video description — Like your title, your video description helps power YouTube’s search function (along with relevant tags), so be sure to make use of this space with good keywords, a compelling description of your video, and links to your website, social profiles, retail store, etc. If you want to get viewers to leave YouTube (to go to your own website, for instance) put that URL at the very beginning of your video description so it will appear
   before the “show more” section.
6. Use an intro — Create a short intro (1-5 seconds) that can be used across multiple videos in a series to provide your channel with a sense of cohesion, continuity, and vibe. You can upload an intro to YouTube as a private video, and then use the video editor tool to combine that intro with any new videos you want to publish.
7. Create HD videos — In the Settings section, a viewer can change the speed and quality of your video, so make sure you upload the highest quality video possible (ideally at least 720p or 1080p).
8. Add End Screens — With mobile-friendly end screens, you can drive more engagement at the end of your videos, directing viewers to other videos or playlists, asking them to subscribe to your channel, offering merch, and more.
9. Put your video in a playlist — Add your video to a playlist and, whenever you share the video, embed the “share with playlist starting from current video” code. That way if a viewer clicks “next,” you can lead them to another one of your videos.

(From CD Baby YouTube guide)