You should be knowledgeable and have an interest in the topic you choose. If you pick a subject you know little about, you will spend most of your time researching rather than creating videos.
YouTube favors channels whose viewers are inclined to watch several videos in sequence. Imagine a series of videos showing the progress of a project, such as restoring a vintage car. Viewers will be keen to watch several videos as the vehicle is brought back to life.
Don't pick an topic that is too specific. Your topic should be broad enough that it allows you to change direction and offer plenty of opportunity for new video ideas. Ask yourself could I create 500 videos on this topic? Two videos a week over the next five years.
Finally, if you have lots of ideas (lucky you!), pick the one that has the largest audience. Use a tool like Google Trends if you are unsure which of your topics is the most popular.
Homework
Draw up a list of ideas for your channel and pick one.
