Michael You probably already know that in America, a period is used instead of a decimal comma. If something costs one dollar and 99 cents, $1.99 is written on the label. By the way, you never write 1.99 $; the dollar sign always comes before the amount. Conversely, in long numbers, a comma is used to separate the thousands: An American writes one million as 1,000,000, unlike the German convention of 1.000.000.
It sounds crazy, but when Americans use quotation marks, they sometimes include the following punctuation marks within them. In German, you write: Auf dem Schild stand "Willkommen", aber wir gingen nicht hinein while in American, it actually is The sign said "Welcome," but we didn't go in. Look where the comma is! Insane! In British English, however, the comma follows the quote, just like in German. If you don't believe it, you can look it up on grammarbook.com
Spelling heroes the Americans are not, by the way. It happens quite often that someone can't distinguish between 'it's' and 'its', and that's fatal because the first is the abbreviation for 'it is', and the second is a so-called 'possessive pronoun'. So the correct spelling is 'It's raining' and 'The horse turned its head'. The same applies to 'they're' and 'their', which are both pronounced exactly the same.