Add useful, original content
No stealing other content, images, games, videos, etc. ONLY use other content with permission and give proper credit (in some cases this credit is an affiliate link!)
So I told you what not to use, how do you create useful, original content?
Write reviews, summaries, blog posts. Create videos, show screenshots, link to content related to your site. Create a blog or a website that focuses on a fetish or niche. I won't go into great detail here, but be creative and bring something unique to the table. Provide free content. TotemCash (VirtuaGirl) and GameBoxxx (3DSexVilla) both provide galleries and movie clips you can post as content to you site. Just be sure that isn't the only content on your site and if you have other resources be sure to get permission if needed or use public domain stuff. Make movies from erotic games or hentai (once again, no copywritten material) and upload them to Naughty Machinima. Then you can embed the video(s) right into your site.
Writing goes a long way in helping your site look professional. Put yourself in the position of the person surfing your site and write something useful for them. If you lack writing skills, consider hiring a writer or two, or just tip the balance of your site to media items. Useful content may be nothing but one or multiple types of media for the user to enjoy. Images, Videos, Flash Games, etc. Make it interactive. Present it with a new twist.
Once you have useful, original content, join these affiliate programs and add the text links and banners to your site before you try to get traffic.
Banners: Don't go overboard with the banner ads, just a few here and there so as to not completely annoy your visitors, and use different ones on different pages. Or look into using a banner rotation script, but it's not necessary if you're not ready to install a complex script as long as you use variety throughout your site.
Text Links: These are best done as recommendations, as in you recommend an adult site or product or game for users to check out and you tell them why. With both kinds of ads, be sure to use the correct affiliate linking code so as to get proper credit for any sales.