membership structure advice needed

I have a membership site, that I’m building, for tutorials and a Q&A forum to help business owners and other sales pros.

I’m not sure if I want to allow visitors to see any of it or some of it, and whether or not to allow for a free limited membership and a premium one, or to do a free trial, for a few days, moving into a premium membership, or just to lock out everyone unless they are a paid member.

I know the free look or free trial seems appealing to give people a sneak peek, but I could do that with a video demo. I plan to implement the affiliates plugin also, so other members will be referring people. I don’t want to overly complicate this, but does anyone have general advice on this topic?