The gods of Google have bestowed upon me a new check for $113.13. The checks are comming more frequently from my pay-per-click ads published on this site. Officially, I'm not allowed to encourage readers to click the ads when they visit, but I can say a big thank you to those of you who did.
This website has a very good click through rate, because the ads are well tailored to the content. Staying niched will help increase your click through rate because the ads will remain focused on your current content.
Many bloggers make the mistake of talking about thier daily lives and straying off topic frequently. When you do this realize that you will need to get far more visitors for the same revenue.
Additionally, many of your topics won't have high rates of pay for each click. Certain subjects have lots of competition for keyword bidding. Because of this, the amount paid per click can be very high, some over $1.00 per click. Other subjects will pay little or nothing for a click.
I don't encourage people to specifically write for the highest bidded keywords, because so many other bloggers do the same thing. They end up diluting the keywords by creating more and more sites focused on high profile keywords.
Write what you like, and find an audience for what you write. The secret to making money with Google is to produce lots of unique content, then generate as much quality traffic as possible.