You have to look as good as I do in my avatar, mate. ... or use common sense. It's kind of obvious how the industry works.
Join an affiliate program in the niche your site is about and put up a banner at the top right of your website.
CPALead used to have an adult program, though I can't remember the name the revenue was great. (Though to be fair I haven't used it in about 2 years.)
Go back to 1999 and put up your site. No but seriously the general adult market is so saturated with free content it's almost useless to have a site unless you have huge amounts of traffic to covert the few that will pay for it. If your still intending to go into this market I would suggest going as niche as possible. The weirder the better. If you don't mind washing out your eyes after your done putting up your site there is still a little money to be made. As long as you stay legal you'll be fine. Some of these affiliates tend to blur that line so be careful. If your uncomfortable by it then you probably shouldn't be selling it. Best of luck to you.
I would say by ads and membership fees. But beware as you have to be very careful to be legit and legal you can take any step any way and BOOM a mistake.
The adult niche is very hard to compete in. Copyright is the biggest issue. The porn producers can and do go out and slam you with DMCA complaints and will try to shut you down if you use their content. They also have million dollar budgets and it's near impossible to rank for those keywords. However, you can make money with CPA.