How to Increase my Youtube subscribers?

Optimize so that it can appear in searches with key words. Besides appearing in Youtube searches, appear in Google searches too with the key words. Besides this, you can run paid ads in Google, social media like Facebook...

That is not enough for a valid question here on Seoforum.

At least tell us what you've already tried and how it worked for you. Always be specific.

Employ "Power Playlists" Post lengthy videos. Use your end screen to promote videos. Watermark your brand, please. Consider the video quality. Answer each comment. Make your channel description compelling. Streamline People to Become "Subscriber Magnets"