My impression of what works based on following lots of youtubers on twitter (who complain constantly about youtube), and from the handful of videos I've seen on the topic:
1) regular uploads. Set a schedule. Rarely, if ever, deviate from it.
1a) If you're planning on making a living from this, super frequent uploads (at least 1 per week) in the early stages. Once you have a patreon base, you can ease off a bit if you want to go more high-concept. For instance, this is basically what all of the big lefttubers did (ContraPoints, PhilosophyTube, hbomberguy, Sean, etc.)
2) good thumbnails and titles
3) cross-promotion and regular calls to action - get a twitter (and possibly an instagram). Post frequently. Follow producers who have audience overlap with your niche. Don't be thirsty or spammy in their replies, but have a presence. Make sure you remind people to thumbs-up and subscribe at least once per video. It seems cringey and weird, but it really does make a difference.
3a) Just because I forgot to mention this originally, but big and easy one: find subreddits that cater to your target audience (especially if there's a subreddit that caters to a specific youtube subculture you're trying to break into), have a presence there. Make posts linking to your videos (assuming it's allowed, typical, and not done in a spammy way).
4) have realistic expectations. If you're making videos on a niche subject or in a niche/unpopular style, recognize that you're probably not ever going to be "big." Look around for other channels making similar content, get a sense of the subscriber range you can expect.
4a) If you want to be "big" (or bigg-er), then look around at what's popular. You don't have to completely abandon your own voice, but it can be really helpful if, say, you're a video essayist and everybody is doing videos on para-social relationships, to do your own video on that topic. (Of course that doesn't matter if you aren't interested in being big)
5) be patient. Based on what I've heard, the first 6 months (at least) of a channel's lifetime are typically very rough. Virtually no growth, often. But if you keep at it, eventually the algorithm will sort of "figure out" what your audience is, and will start sending new subscribers your way (a big reason why steady, frequent uploads, especially early on, are important). Once that "click" happens, you'll see steady gains for awhile until you sort settle at an equilibrium. From there, the sense I get is that further growth depends on other factors: is your quality and quantity still consistent/improving, was your growth part of a trend that is fading, do you have a presence and sizeable following on social media, did you have a viral hit? etc.
I will check it out and subscribe
