With a decent amount of content and traffic on your blog, you can start considering implementing Google Adsense contextual advertisements to start earning an income from your website.
The best part of using Google Adsense is that Google will do the job of placing the most appropriate and relevant advertisement on your page based on the content on your we page. This will not only increase the chance of the advertisements getting clicked / viewed but also provide you a consistent earning.
Personally, in m initial days of blogging there were months for which I never received a single penny from ads and I was not sure when I am going to start making money, today I receive up to 50 USD a single day from Google Adsense alone! The open secret one should know and accept is that ONLY with a decent traffic (approx 10000 unique visitors a day) you can even expect earning from Adsense.
Comparing Google Adsense Image ads with Text ads: analyzing success of ad units and ad types are specific to the niche, audience and several other factors however, from my experience I have observed that large image and flash ads catch attention of readers easily and have more chance to get noticed and clicked.
When you have large text content on the page, blending tex link units to the design can also help improve the CTR or earnings from Google Adsense. Let me know if you have already started to use Adsense, if yes let me know your experience.