In order to increase engagement on YouTube, it's a good idea to give your viewer clickable links at the end of your videos.
In this example I've linked to a related video, and to a Subscribe Button
Here's how I set it up in Final Cut Pro X:
On the timeline add a short clip from another video, and add a subscribe button.
After uploading the video to YouTube, you have to add ANNOTATIONS.
Use SPOTLIGHT MODE.
Then CLICK 'Link', SELECT 'Video', and add in the URL of the other YouTube video.
YouTube: How to Link to another YouTube video, in a video
Here you CLICK 'Link', SELECT 'Subscribe', then add your YouTube channel name.
YouTube: How to Add a SUBSCRIBE button to your Video
Here's a subscribe button you can use:
Image: YouTube Subscribe Button
See these links in action here.