In terms of tab and box labeling, see if you can isolate 'trigger words'. These are essential words that increase or create information scent for the user. Information scent – a term coined by noted usability guru Jared Spool - refers to how well links and navigation match a visitor's information need and how well they predict the content presented at a link's destination. Trigger words are navigation labels and text that match the visitor's need on your guide.
Effective navigation also shows the "aboutness" of a guide. Whether you are using tabs or a table of contents model, your choice of labeling should advertise clearly (and as concisely as possible) what content can be found there.
Navigation design is about creating patterns that people get accustomed to. Strive to create a consistent user experience especially if you are creating a series of guides that you suspect will be used by the same users. Where possible, give cues of what will happen when a user clicks on a given link and then help reorient them when they arrive at the new destination.
Some questions to ask yourself regarding the navigation experience of your LibGuides: