The first key to understanding SEO is to understand why it's so vital. As video creators, we must understand how to get other people interested in our work. And we do so, by showing interest in them.
Search Engine Optimization is the art of making search engines believe that your content is relevant and important. If you can do this effectively, you can expect to see more viewership and engagement on your YouTube videos.
Strategy without tactics is the longest route to victory. Tactics without Strategy is the noise before defeat. Before you launch out into creating content, be sure to sit down and map out the strategy and the plan to get you to your destination.
Now we begin to move from strategy into the tactics of Search Engine Optimization. Remember your title is the launguage of your video's billboard. Ensure it entices your viewers to click by making it interesting and congruent.
Your description is extremely important from an SEO perspective. Do not get lazy here. Write as much as the metadata field will allow you to write using plain English that properly describes your video (remember: AVOID KEYWORD STUFFING). I've had videos explode with viewership because I took the time to do this step correctly.
Don't overthink tags. Just get enough in there to properly categorize your video with YouTube's search engine. DON'T FORGET TO PUT YOUR CHANNEL NAME IN YOUR TAGS. Tags DO help your videos appear in suggested video results.