You already know that allowing your videos for monetization is one of the things that you can do so that you can start earning money, but another thing that you can do is to connect your YouTube channel to an AdSense account. This will allow you to earn a lot of money whenever people view your videos. If they would not skip ads, you may actually start earning.
Another thing that you can do is to know the type of videos that can be monetized the most. There are some that will not have a lot of audiences, so the chances that the videos will be monetized will not be too ideal. The more you know about what can be viewed on YouTube, the more that you can come up with content that people like.