[brothers4thID]

There should be two spaces after a period.

One of my pet peeves is the em dash vs the en dash.

Johnny wants the red car — fire-engine-red if he can find it — instead of the blue car.

Of course, this is made much harder by the lack of a true em dash key on modern keyboards.

[SgtHooper]

Yes, you are correct, two spaces after a period. Let’s reiterate this again for everybody.

[cartan]

Johnny wants the red car — fire-engine-red if he can find it — instead of the blue car.

Isn’t proper usage without spaces around the mdash?

Johnny wants the red car—fire-engine-red if he can find it—instead of the blue car.