Something I have found effective is advertising to your target audience. Depending on what you are uploading, try sharing your channel in communities that you revolve around.
Something else that is effective in videos are call to action techniques, where you call for your viewers to do something, such as, like your videos, comment, and or subscribe. You can do this by adding graphic overlays, annotations (don't make it too distracting), or just saying it in your commentary. You can also include some call to action in your description.
You should also try to make people want to watch your videos. To do this, having things like a good thumbnail will help. Try to find something that will really get people excited and want to click on your video. Have a good title also helps.
Make sure your channel and videos are of the best quality. Make sure you have a clear mic, good quality recordings, and don't let your videos drone on. You have to have a good personality, and good editing skills. Keep the viewer entertained. One of the hardest things of being a YouTuber is keeping the viewer watching your videos. You will have probably noticed that the user retention time on your video isn't super high. To keep viewers interested, make sure you always have something to say. Whether you're cracking jokes or telling a story, keep the commentary alive.
Another way to keep the viewers interested:
Keep your videos short. Sometimes, especially with gameplay, less, is more. Take only the best parts from your game play and or commentary to put into your video, so you can be sure the viewer stays to watch. Make sure your edits are clean and of high quality as well.
One way to entice your viewers to subscribe is with a high quality banner and profile picture. If you can't make one yourself, get someone else to. That has more skill in that area. Personally, if I see a YouTuber with a bad banner, I am less willing to subscribe.
To get your channel and videos suggested across YouTube or found in search results, include tags and words in your title, descriptions, and tags, that are relevant to your channel and or video(s). That way, you are directing your videos towards specific viewers. The ones you want to watch your video.
That's all I can say from my experience!
I hope I helped.