If you have experience with SQL you might be far better off than I was. Try starting with the book in this thread; it seems like an excellent starter book and covers many concepts that frankly, myself and others had to piece together from Stack Overflow questions.
The best advice I can give you is to start with a project; what do you want to make? If you're set on Rails, jump into Ruby using the nice online book Learn Ruby the Hard Way. Consider checking out Rails for Zombies for a nice, fun intro into Rails and then dive into the book listed in this thread.
Best of luck! Feel free to reach out if you have any questions!