The Gutter
The inside margin where the pages are glued (the spine) needs extra space. If your text is too close to the gutter, it will fall into the crack and be unreadable. Add at least 0.125" to 0.25" extra margin on the inside edge.
Page Numbers
Odd numbers are always on the Right page. Even numbers are on the Left. Ensure your pagination reflects this.
Fonts
For body text, serif fonts (like Garamond or Caslon) are generally easier to read in print than sans-serif fonts.