My class recently covered the importance of navigation flow and guidelines to create a proper navigation flow.

These are some of the guidelines:
-The most important information should be at the top, left hand section of the page.
-A flow should be created from top to bottom, or left to right.
-Alignment, grouping, and borders can be used to assist in navigation.
-Always direct the user's attention to the most important item.

Usability guidelines were also covered in class:
-Easy to read fonts and colors should be used.
-Ensure that all pages on the Web site have a consistent look and feel.
-Lay out the content properly and make sure to use white space to guide the user's eyes

You always want to make sure your design enables as many users as possible to benefit from your web services.