Navigation that works should:

• Be easily learned
• Remain consistent
• Provide feedback
• Appear in context
• Support users’ goals and behaviors
• Offer alternatives
• Require an economy of action and time
• Provide clear visual messages
• Use clear and understandable labels
• Be appropriate to the site’s purpose

Bullet points provided by Jennifer Fleming’s old but still relevant Web Navigation: Designing the User Experience (1998). I wore that book out reading and rereading on the bus ride to my main gig then.