"Subscribe to see more videos from this channel. You've recently watched videos from [channel's name]. Subscribe to see their next videos right here on your YouTube homepage."
You can subscribe to the channel or hide the message by clicking the small "x" icon.
Now that you've subscribed to the channel, you can change your subscription preferences when you watch a video from that channel. There's a wheel icon next to the "subscribed" button that lets you enable email notifications and restrict the subscription to new uploads.
If you need more suggestions, check the "recommended channels" sidebar from YouTube's homepage or visit this page. Remove the channels you don't like to improve YouTube's future recommendations. Mouse over the channel's thumbnail and click "preview" to check some of the recently uploaded videos. Use the arrows to navigate between YouTube's recommended channels.