1. Get a domain and hosting
2. Install wordpress and start posting clips, movies
3. Put ads on your blog to earn money.
If you need more details, reply.
It depends on what kind of a porn blog. There are few types of porn blogs:
- Steaming porn blogs
- Copyrighted porn blogs aka the warez blogs.
- Amateur porn blogs
- Blogs with only picture collections
Best thing is to go with the amateur porn content since it's not copyrighted, and you can host your site anywhere you want.