Word gives you many hyphenation options. I prefer to hyphenate manually so
that I have more control. To do this, use Ctrl+Hyphen to insert a
"conditional hyphen." This hyphen will be displayed only if Word breaks a
word at the end of a line, so if you add or delete text in such a way that
the word you hyphenated ends up in the middle of a line, the hyphen will not
print.

You can also have Word hyphenate for you automatically. This is controlled
through Tools | Language | Hyphenation... You can set limits on how much and
how often Word hyphenates; this may take some trial and error to fine-tune.

A compromise between fully automatic and fully manual hyphenation is the
Manual... button in the Hyphenation dialog. If you click this, Word will
step you through the document, allowing you to accept or reject its
hyphenation suggestions (based on the settings in the Hyphenation dialog).