(Navigation) gives us confidence in the people who built it. Every moment we’re in a Web site, we’re keeping a mental running tally: “Do these guys know what they’re doing?” It’s one of the main factors we use in deciding whether to bail out and deciding whether to ever come back. Clear, well-thought-out navigation is one of the best opportunities a site has to create a good impression. | Don’t Make Me Think by Steve Krug

To design a good navigation put:

• The Site ID (logo), better if in the top left, the easiest place to spot it for a new visitor,
• a Home button, it makes life easier for visitors,
• a search function, I hate it but Steve Krug push a lot for it, he knows better for sure,
• Sections with more-than-easy-to-understand names, no creativity, it’s a map not a riddle, (ah better to align them on the top right),
• an indicator (link color, background, underline) to highlight the current position on the navigation.

Make the navigation always visible.

With the exception of landing pages (especially a Sales page).

These Public notes are also an exception. The purpose is to create a mental flow.