In order to start making money on YouTube you are going to have to do more than just sit in front of your camera and talk. You are going to have to build up a viewer base, by either vlogging about something you are passionate about, or finding something else to talk about that people are interested in. Many of the top YouTubers today follow the vlog format, on a schedule similar to television. All these YouTubers did not start with the subscribers they had though. They worked hard and pushed out video content almost everyday to give users an incentive to subscribe to their channel. Not every YouTuber has been so legitimate with their subscribers and views though, many used automated programs, also known as bots, to increase page and video views. Artificially boosting their videos to top watched and receiving more recognition than they deserved.
Now I'm not saying you should do anything illegitimate to build your viewer base but some of the most well known YouTubers did just that, and they are now profiting largely off it! After you have decided what you are going to vlog/make videos of and have built up a subscriber base of 500+ unique users you will want to apply for YouTube partnership. Only apply for partnership once you have uploaded a good number of videos and the total views for each video is in the thousands. Also make sure that you frequently upload new videos, YouTube will decline your application if you do not regularly upload new content. Another sure fire way to make sure your application gets declined is to have copyrighted material on any of your videos. Any music, or video content that you use that is not of you must have written consent from the original author.
If you follow the guidelines above you should get accepted by YouTube to become a partner, if you have not yet signed up for a Google AdSense account now is the time. Once you get your Google AdSense account up and running you can start placing ads on your videos. Each click that your ass get will generating revenue, while not much (often just a few cents per click) it adds up when you have thousands of people clicking the ads. Many of the top YouTubers report 6 figure incomes, just from making YouTube videos a couple times a week. If they can do it, why can't you?