There are many ways but the six things i would definitely suggest you to do are :
- Ask a question in your video description
- Always reply to comments. Ask a question back if possible
- Always ask views to post a ‘like’ and a comment, either good or bad!
- Ask questions or place comments on other peoples videos that are in the same niche as your video.
- Post a url ink to your video on Facebook, asking for comments.
- Start conversations by commenting under other videos in the same range of videos like yours.
- Buy Youtube comments. Buying YouTube comets will definitely help you increase your channel’s growth and help your channel over the long haul. A lot of new channels face a lot of problem at first for getting likes, comments and subscribers. Because YouTube users only subscribe and comment on those channel that are popular. In spite of uploading good content their channel doesn’t get visibility. So if they buy YouTube comments and likes then they will be free from these initial struggles and can focus even more on their content.
One of the best and trusted sources to buy YouTube comments is promoting team. So if you are interested then do give them a visit.
I hope I could help you bit.
Good luck and just keep on doing YouTube, you'll see the comments will increase over the time a way!