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My suggestion is to put a "custom block" on your index/home page. In this custom block, explain what your site is all about and give instructions on how to find information they may find helpful. Some people are just lazy and others are just uneducated on the ways of surfing the net. Educate the uneducated with some guidance. The lazy one? Well, they either click their mouse a few extra times or they miss out on information they wanted.
By doing this, your visitors will more fully understand your site and search engines may respond a little better when indexing the content.