It is very hard. I have a dating site and get about 1000+ page views per day and have only had it for about 2 months, but do not worry about the adsense, worry about getting the traffic because it is very competitive and it will take money to make it!!
Use the AdSense guidelines and base your ad placement on the AdSense guidelines. Another way for you to increase your AdSense placement goals is to embed your ads in pictures and change the look in order to make the ads seem as though they are a part of the navigation. As for building traffic, link building is king -- I compiled the link-building ideas into one article on my one site. Also, think about an SEO affiliate program (iDevAffiliate Pro comes to mind) and constantly test for conversions on your pages.
Thank you all for your replies. My dating website is really new. And I wanted to feel the whole picture with adsense. You replies helped me to understand, to see the whole picture. If any one has something to add or say please do it , I am checking my thread often. ----------------- Can you tell me please, if it is not a big secret probably how many users could you get in 2 months. Can you share your practise with me in PM. My web dating site is intented for locale use first ( in my own country I mean). Thanks