Add content. Try to upload content that is high quality, and isn't super long. (This option can vary depending on what type of content you decide to upload) Also try to upload regularly and stay consistent with your uploads.
Even if your content isn't great at first, keep at it. Practice makes perfect. Try to make each video better than the last. You will often learn as you go.
Improve your content by either using a better camera or trying better editing software or techniques. Also try to improve the way things are filmed. Use a tripod, have a friend help you or light your scenes better. It all helps for a better end product which in turn helps you get a better audience.
By uploading regularly you can help hold an audience. People are more likely to subscribe if you add content on regular schedule, and maintain that schedule as much as possible.
Make sure to tag your videos with key words that describe the content, as well as an eye-catching description. These will help drive people to your video from YouTube searches.