A compound sentence is usually made up of: Independent clause + coordinator + independent clause. Usually, there is a comma after the first independent clause. We use the FAN BOYS coordinators to form compound sentences. For example:

for

I prefer living in Shizuoka, for Tokyo is too noisy. (The second clause gives the reason for the first.)

and

Shizuoka has the ocean on one side, and it has the mountains on the other. (The two clauses express equal, similar ideas.)

nor

People in Shizuoka do not have to travel as far to work, nor do they have to put up with extremely overcrowded trains. (The two clauses both contain negative ideas.)

but

Tokyo may have more excitement, but Shizuoka has more peace. (The clauses contain equal, contrasting ideas.)

or

People in Shizuoka can easily spend the day at the beach, or they can spend it in the mountains. (The two clauses contain equal alternative ideas.)

yet

Young people love the action of Tokyo, yet they want to move out once they have children. (The second clause is a surprising, unexpected contrast to the first clause.)

so

The shinkansen runs through Shizuoka, so we can easily be in Tokyo in an hour. (The second clause is a result of the first clause.)

Adapted from: Writing Academic English 3rd Edition by Alice Oshima and Ann Hogue, White Plains, NY: Addison Wesley Longman, 1999.