You need to make a mobile version of your site. If it is Wordpress, you use a mobile theme, if you are using Mech Bunny or KVS, they have their mobile versions too. If you are planning to work on a website, you need to make sure, that it will be possible to have a mobile version too.
After that, you need to work with websites like
Bitter Strawberry, and
Sex Goes Mobile, as these companies are the most profitable, and the best. Mobile popunders from
Plugrush are a very good addition to the mix too. If everything is set up correctly you should be making around 50% of your income from the desktop version, and the other 50% from the mobile version of your site.
Other companies to consider, for the mobile part, would be
First Mobile Cash, and
VPS Mobile. Not all companies are the same, and they may turn out to be better and more profitable for some of your xxx sites.