Focus on having a quality video first. Once you have that, make sure to have multiple on your channel. The more videos you have to work with, the more YouTube's algorithm has to work with. And when viewers see one good video and they want more, if you have none.. well, you're losing out on subs.
Once you have a base built, then you can focus fully on marketing. But before then, fully utilize your channel by having a bunch of quality uploads AND playlists, deck out each description of video and your channel, have a custom logo and background, use intros/outros, use annotations and cards to link to other videos/playlists and encourage likes/comments and subs. The more engagement, the better it'll be ranked.
Do good SEO by using keywords multiple times strategically in the title, description, hashtags and even when uploading the video file (correctly naming it). Use colorful thumbnails as clickbait (proper clickbait isn't spam if it's actually in the video). Use clickbaity titles, but nothing too spammy. Engage with all comments and encourage them to calls of action.
Then onto marketing. Promote on reddit and other platforms. For reddit you can use upvote groups or buy upvotes to get to the top of good threads. Be careful though, they HATE spam so make sure it's good. Pay for shoutouts and targeted promotions. Maybe buy PPC ads on YouTube itself. Collab with other people. Post on forums and other places. Share it with friends and family and virtually everywhere you can.
Rinse and repeat with every video until one finally goes viral.