It's important to know who your fans are, and it can be even more valuable to know who your channel's most influential subscribers are. Identifying those subscribers that have massive followings can help you explore novel ways to reach new people. If someone has taken the time to subscribe to your YouTube channel and wants to stay up-to-date on your latest videos, there's a good chance they'll find your content valuable enough to consider telling their fan base about it.YouTube provides a great resource to help you find out who those influential subscribers are with the Subscribers page in the Creator Studio. By logging into your account and going to that page, you'll see a list of all of your channel's subscribers ordered by the most recently subscribed user. You can choose to sort by the most popular subscriber, which will show you how many people follow each of your subscribers and how long each of your subscribers has been following your channel. What's also cool is that YouTube provides direct links for you to subscribe to those people that have already subscribed to your channel, as well as the ability to send them a direct message. This is extremely helpful if you want to reach out to the most popular YouTube users that have subscribed to your channel.
Consider contacting some of your channel's most influential subscribers to see if they're down to help spread the word about your channel or to possibly collaborate in an upcoming video of yours. If you approach them in a non-spammy way and present a few specific ideas on how you could collaborate and how you could also bring additional exposure to their channel, there's a good chance you'll find other video creators that are willing to help you succeed in reaching new viewers.