An independent clause contains a subject and verb, and conveys a complete thought. It is a sentence in its own right.
When joining two independent clauses without the use of a coordinating conjunction (and, but, or, or nor), use a semicolon.
Or treat the clauses as separate sentences.
Do not use a comma in the absence of a coordinating conjunction.
Overuse of small sentences can affect the flow of your writing, resulting in Dick and Jane grade school primer-type text. The use of semicolons can help eliminate this and can align sentence content more closely. However, semicolons should be used sensibly. Be sure that the independent clauses involved are directly related, and take into account the balance of the clauses in terms of length and import; otherwise treat them as separate sentences.
Sources: The Gregg Reference Manual; Fumblerules by William Safire; the Internet