1. You must have good content. That goes without saying. If your content is rubbish, people won't watch your videos to the end.
2. You must make sure that the title is clear and to the point and you have the right key words in the description. Initially you won't appear on people's home pages but they will find you if they search for a video on a particular topic and words and phrases in your tags and description match their search.
3. You must have good thumbnails and titles so when your video comes up in the search people can immediately see what it's about and that it's just what they were looking for.
4. Don't worry about the number of subscribers. If you do all the preceding steps correctly, the subscriber numbers will grow naturally, but chasing subscribers and boasting about how many you have won't get your channel higher in the YouTube rankings.
YouTube promotes channels based on how many people click on the videos (click through from the search) and who then watch the video right to the end. You can get masses of clicks via clickbaity titles, but if the content doesn't appeal and the viewers only watch a moment or two, your channel won't grow.
And one final point, from observation of channels with lots of subscribers and views, it seems it helps to speak really really fast, say, "super awesome" a lot and wear a baseball cap backwards. Well, not really, but a lot of the very popular guys seem to do that. :-)
Because my videos are in Welsh but people may search for them in English, this will require a bit of thought, but I need to do much better than at present.
This is also where I need to do a lot of work because I hadn't realised the importance of this and though the pictures I've used for thumbnails are OK, some could be better and I need something catchy in the way of a title on the thumbnail.