I know, earning from Google Adsense isn't really that easy, unless you have a really high-traffic site. But, it is doable.
Two things you can do to boost your earnings include:
1) Placing the ads in a prominent place, like before every blog entry or at the top of your sidebar.
2) Limiting the ad spaces in your blog. Learn from the law of supply and demand, the more space you make available, the lesser the (demand) value will be put in it since advertisers need not compete anymore for that place of honor.
Make the necessary changes now. And 'label' your adsense codes appropriately so you can easily see which ads are generating income and which ones should be 'hidden' already.