Some tips...
1. Put a opt-in form on your website, and put the opt-in form above the fold
Put a opt-in form can capture visitors' emails addresses easily and you can easily use email auto responder like aweber, mailchimp to send emails to their inbox to get them come back to your website.
For most of the visitors, they will only visit your website once, and they just leave forever and will not come back to your website again. Hence, emails and facebook are the 2 things that people checked almost everyday. Hence it is very important to get all your visitors' emails.

2. Put a facebook like box on your website, it attracts your visitors to like your facebook page.
Once they liked your facebook page using their facebook account, they WILL receive any messages on their facebook new feeds once you post any messages on your facebook page, hence it is very useful!
You do not need to pay for anything like email auto responder, or bulk email sending services, you can just send the messages to their facebook new feeds, and they will see the message (adsense niche site URL..).
http://developers.facebook.com/docs/reference/plugins/like-box/
3. Make sure your website has done a good SEO (on-page and off-page)
Good SEO will make sure your website ranks on top of the search engine and get passive traffic everyday, and please remember that traffic coming from Google is very targeted and they will likely click on your adsense ads as your adsense ads is a contextual ads will change according to your content.
For example, they searched for ''acne scars treatment'' on Google and they saw your website on Google SERPS top ten and they clicked and entered your website, the first thing that they will see your adsense ads, and the adsense ads is also about acne scars hence they will click on the ads immediately. CTR increased...
These are the 3 golden tips to get your visitors coming back to your website repetitively again and again. Why? Google, facebook and emails are the 3 things that people always check when they first start up their computer.
