There are some
1- Thumbnails : are very very important for your content on YouTube because its show the quality of your content which people sees first.
2- Title : is most important step in seo. Choose and used important keywords in your video title.
3- Content matches title and your video thumbnails : The title should not be too different from your thumbnails otherwise it would be the waste of your time. Together they will blow your video viewers.
4- Content plan : here its on you how you put your content or used your content in your youtube video. Here you can give some information etc ...
5- Call to Action : call to action means to tell viewers to subscribe , like or comment in the video.You can written as well as verbally tell your viewers to subscribe my channel.