The semicolon is used between
independent clauses not joined by a coordinating conjunction but
too closely related to be separated by a period.
You may, however, use commas if
clauses are short and parallel: E.g.: I'll talk, you listen.
Semicolons are not a
substitute for the colon. Be aware of and avoid confusing the two:
a colon marks a list or explanation; a semi-colon announces a
related, full sentence will follow.
Be sure to review your textbooks
and English manuals for more information; nevertheless, make sure
you need to use a particular punctuation mark and aren't
just using it as a practice.
Avoid "semicolonitis," a rare
condition marked by frequent and inappropriate use of the
semi-colon. Semicolonitis is cured through a thorough review of
punctuation rules and a complete ban on semicolons for at least
two assignments!