Use a semicolon
1). To join two independent clauses that are closely related in meaning
Some visitors thrive on activities; others seldom leave the lounge.
2). To join two independent clauses when the second begins with or includes a conjunctive adverb, such as however, for example, or in addition
Everyone agrees that nuclear warfare is horrible; several nations, however, continue to manufacture nuclear weapons.
3). To seperate main clauses linked by a conjunction if commas appear in the clauses
Early in the play, Samson, tormented by his bondage to the Phillistines, his blindness, and his fall from glory, laments his condition; but he is careful to blame himself, not God.
4). Between items in a series when one or more of the items include commas
The furniture consisted of a bed, with four large, shapeless pillows; five matching wooden chairs with upright backs; and a corner cupboard imported from Bristol, England.
Do not use semicolon
1). Between a phrase and the clause to which it belongs
We tinkered with the wiring of the loudspeakers; to increase the volume - Use of semiclon is incorrect here.
2). Between a subordinate clause and the main clause
Even though I was exhausted; I listened to his complaints for two hours.- Use of semicolon is incorrect here, we must use a comma here.
3). A semicolon to introduce a list
Her house has four rooms; a kitchen, a parlor, a bedroom, and a bathroom.- Use of semicolon is incorrect here, we must use a colon here.