Is your document full of it?

Ah, underfull and overfull hboxes and vboxes in latex.....

You can do certain things:
a) if they look fine - disregard those warnings
b) for overfull/underfull hboxes, you need to rewrite the line that has the problem (latex will report it), or resize the figures (if they are the cause) accordingly
c) for overfull/underfull vboxes - you need to either allow some flexibility in the interline and/or interparagraph spacing (e.g, give \baselineskip, \lineskip, and
\parskip some stretchability), or else tell LaTeX that you want \raggedbottom pages. Underfull boxes are a consequence of not enough flexibility in the vertical spacing, and lines that don't happen to exactly fill the page size. Just type \raggedbottom at the beginnning in the preamble, and that should cure underful vboxes.