Numbers
Another mistake made by people faithfully following the pictures in most illustrations of the ASL fingerspelling alphabet is the signing of the cardinal numbers 1 - 5 with the palm facing out. The cardinal numbers 1, 2, 3, 4, and 5 should be signed palm in (towards the signer). This is in contrast with the cardinal numbers 6-9 which should be produced with the palm turned to face the person being addressed.
As with the letter O, the zero should not be turned to the side, but shown palm facing forward.
This applies only to the cardinal numbers however. Using numbers in other situations, such as with for showing the digits of the time for example, has different rules. When signing the time, the numbers are always facing the person being addressed, even the numbers one through five. Other signing situations involving numbers have their own norms that must be learned on a case by case basis.