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Reviewing analytics and running usability tests are the two best ways to decide how much to have in each navigation system. There are several different forms of usability tests that you could use to determine the best way to organize your website and how to label each page: TreeJack is a service that will let you try out different navigation menus to make sure people can find what they're looking for; you could do card sorting which gives people a set number of categories but they physically or virtually group the cards into categories and you can then use the categories in your navigation; you can even create prototypes with a tool like Axure or Balsamiq and have people try out a few different options to see which one works best. If you don't have the time or budget for usability testing, looking at analytics is second best. Things to look for: what content is the most visited on your website? Are people getting there by navigating through your website, or are most of them coming directly from organic search to those key pages? How long do people spend on particular pages? If some of the pages have very low time on site, it's a good idea to shorten the navigation path - you can either deep-link to those pages in sitewide navigation or just look at specific pages and add smaller nav menus within say a sidebar or a CTA button within that page's content, which gets people from that page to a deeper page with 1 click versus drilling down through several different links one at a time. Another great place to look: if you're tracking site search, see what people are searching for and what pages they're searching from the most. If 75% of people who visit the homepage search for 1 of 3 terms, then put prominent featured sections about those 3 terms right there front and center to help them get there. Also take note of the specific keywords people are searching by and use those as your navigational labels - that can be even more helpful than simplifying hierarchy, if you name things the way people use them naturally. In my personal experience it's best for SEO as well as for users when you stick to the old no-more-than-100-links-per-page rule. If you provide too many options, people just get overwhelmed and don't know what to pick. So my own rule of thumb is to only link to about 5 top-level pages in my sitewide header navigation; under each of those have no more than 4 to 5 sublinks, and leave it at that. But I always make it very, very easy for them to drill down deeper - if the site is 4 or 5 levels deep, those 4th and 5th levels are accessible from the 2nd and 3rd directly, so they don't have to click 5 times to get down 5 levels - they can hit the homepage, go to a 2nd-level page, and from there straight to 5th-level if that's what they're looking for.