Increase the traffic:

Here is the most important part which directly affects the Adsense earnings--->traffic.
It is not easy to get healthy traffic to your website/blog,but here are some tips which work good:
1.Unique content:If you have original and unique content,the search engines will love your website.If you have copied the content from some other website, search engines will neglect your website.Fresh content affects your website traffic.
Example: If you have a website whose topic is "Cellphones", then try to write about each product from the customer point of view.If you compare the similar looking phones with some pictures, the visitor will like it.If you show visitors the camera picture quality rather than just giving it's specifications, they will appreciate it.

2.Search Engine Submissions:Submit your website/blog to different search engines like Google,Yahoo,MSN.
Here are the links to do so:
Google-----> click here
Yahoo-----> click here
MSN------> click here

3.Build inbound links:Inbound links in short mean "getting visitors from other website".
Just search in Google for the topic of your website/blog, find other sites which have similar subject as that of you.Contact the website owner and tell him/her about keeping a link to your site on his/her site.This kind of link exchange will help you in getting you the inbound links.