If you ask me “What part of SEO process is most difficult?”, I would say – Off-Page Optimization. Now thats a very broad topic in itself in SEO. If you ask me “What Part of the Off-Page SEO Process is Hardest for You?”, It is Link Building for me.
Acquisition of Quality Inbound Links / Generating Quality Back Links is one of the toughest parts of SEO Process most SEO Experts face today. Here I am talking Quality and not Quantity. If its not done properly your site can even get penalized.
When I interviewed a couple of SEO Guys asking them this question, some told me “Keyword Research”!!! I wonder why because that’s one of the most interesting steps in your campaign when you are actually learning what your client’s site is all about.