SEO is not easy to learn. From the first sight, it seems easy and fun. But a professional SEO work has to be very comprehensive and detailed, and therefore the training should be very professional.
If you want to learn SEO online you must create yourself a solid basis. After you complete reading and understanding the basics, you should manage an RSS reader, containing updates from major online marketing websites and SEO blogs.
The best basis to my opinion is the SEO Book, written by Aaron Wall. This is a thick book containing lots of information about SEO, SEM, Web Marketing and PPC tactics. This is a great place to start!
