You set tabs in styles. If you want these tabs available in every style, set
them in Normal style (and be sure to check "Add to template" so the change
will be written to Normal.dot). Note that the default tab interval is 0.5",
so you could set one at 0.25" and automatically have all the rest except for
the right tab at the right margin; once you set that, you wipe out all the
automatic tabs preceding it.

I would think twice, though, about setting a tab stop every half inch. What
will you use them for? You should never use the built-in tab stops if you
have to press Tab more than once to get to one; you should always set custom
tabs instead. See http://word.mvps.org/FAQs/Formatting/SettingTabs.htm.