Optimizing traffic channels is ongoing work & and you can always find areas for incremental improvement, but making smart adjustments to site navigation can be a faster route to bigger growth because it simultaneously improves the experience for visitors through all channels.
This SlideShare talks about how several retailers present their categories via top-navigation. I open with a little info on the Pareto Principle because I want people to check their data and understand what categories really influence their business. But the main goal of the deck is to get you thinking about your navigation as something customizable and optimizable.
If you take nothing else away from this deck, remember that you should take a proactive approach to labeling, organizing and emphasizing your content. Navigation can be so much more than an alphabetical list.