Then there's your main opening. Don't go there all cocky, ranting about how bad things are with their current site, as you'd probably just come across as a bit of a twat; instead, explain that you've done some research, looked into how YOU could improve their site, which in turn would improve their custom, and lay down a well laid out plan. It's shows you're pro active, it'll show that you've done your research, and will also show that you understand what's needing to be done.
Be sure to wink at them after you say it!!!! lol
There's some nice tips you got there. If they're amazed at your level of knowledge and ever ask "How do you all these stuffs?" Say "That's just one side of me" like Susan Boyle.