[This originaly was my answer to a post on another forum, but I though it actually deserves to be posted here too!]
How to make $1000/month with blogs (*)
0- Find a theme for each blog that's not too broad. "Big natural tits" is a good niche, so are "black shemales" or "strap-on femdom", but try to avoid just "mature" or "teen". Don't bother making posts about anything not matching the niche you chose. Don't link to paysites selling anything else either. If you want to talk about all aspects of a niche (say BBW), make several blogs: one for "BBW teens", one for "BBW matures", one for "Busty BBW", ...
1- get your own hosting and your own domain (NO FREE HOSTING! EVER!), and install wordpress on it.
2- at least once per week (and not more than every other day! If you have more time on your hands, make more blogs) make a post: At the very least 15 lines of hand-written text (NO RSS FEED), and some images. If you get carried away and type a 50 line-post, that's fine. Never show more than 10 pics per post. Don't bullshit the surfer with crap "click here to buy NOW!" sales text. Show you know your niche well and think of the surfer more as a friend that as a client. (ie: think "convincing a friend" rather that "sale"). Show your personality and every once in a while talk about something else: Wish your readers a happy new year, remind them of Valentine's day a few days in advance, etc... Be creative. Your site should appear to be done by a FAN and not by an AFFILIATE! No blind clicks to sponsors! EVER! If you show a picture, always make it resizable so the surfer isn't left only with the thumbs to look at.
3- Never ever link to a site with a "Free Porn to Advertisement" ratio higher than your blog. That basicaly means toplists, linklists, other blogs are ok; but TGPs, "Tube sites" or TGP galleries are not. Yes that means you should turn down(nicely!) hardlink offers with TGPs.
4- every month or so, try to make a few more hardlink exchanges. if you have several blogs on close subniches and can make abc or abcd link exchanges do so. Try not to add too many links in a too short timeframe. (up to 3 link exchanges per week seems reasonable) Don't exchange links with sites not related with your niche.
5- Follow all that for at least 1 year. if you need to take a break or a vacation you can use Wordpress' post scheduling option to write 4-5 posts in advance and only have them appear online when you want it to.
6- make sure you really understand and follow rules 2 and 4. I mean it.
7- most porn fans follow closely what's happening in their niche. So write about what's new (a performer who make solo for a long time and just made her 1st HC for example; but don't bother making posts about sponsor content that's been everywhere since 2003). Yes, that requires you to follow your niche and watch at least every week the updates on the 5-6 major sites of that niche.
Follow these rules on at least 3 blogs and I'm pretty sure you'd be making at least $1k/mo after 1 year. It may not seem much, but once everything is set up, it only really requires to write 3-5 articles per week which shouldn't keep up busy for more than 1 day at most.
If it doesn't work, PM me and I refund you 100%! No question asked!
Yes, there are people making as much money (possibly much more) using thousands of free hosted blogs automatically fed only via RSS feeds. I just happened to do well using the opposite way :-)
(*): Been there, done that.... (and then some...

)