Leave at least .5" margins on all your pages. Most books will require a gutter of .2" to .3". A gutter provides a little bit of extra margin on the spine edge of your pages, making your book easier to read without putting too much stress on the spine. For coil-bound books, the coils bite about 5/16" (8mm) on the spine edge, but we would suggest a gutter of 3/8" (9mm).
Follow these directions to set your margins:
Microsoft Word: Choose Page Setup from the File menu, then use the Margins tab. When adding a gutter, make sure to select Mirror Margins. Apply your settings to the whole document.
Microsoft Works: Choose Page Setup from the File menu, then use the Margins tab. Works has no provision for a gutter.
Open Office: Choose Page from the Format menu. To create a gutter, add the desired gutter to the inside margin dimension. Then select Mirrored under the Layout Settings, Page Layout choices.