Mari:
How do you handle Dodge when it comes to dodging bullets?
That's likely to end up being scenario specific. GURPS Basic assumption is that you Dodge from where the gunmen is aiming, not the bullet itself exactly.
There are more realistic rules which prohibit Dodging bullets, but those are optional.
quote:
Is there a distance where you simply cannot see if someone is shooting at you?
Yes. That's not likely to come up in the Cowboys and Indians scenario though as it's far enough away that you cannot see the shooter. Or, if the shooter is clearly behind you and started there, making it an Attack from the Back, thus denying defenses (but that happens in melee as well).
quote:
Is it possible to dodge when on horseback?
Yeeesss.... hmmm. Let me double check.
Ah here's the relevant rule:
GURPS Basic pg 398:
A rider can Dodge, Block, or Parry. If he has Riding at 12+, all of these defenses are at normal levels. For a less-skilled rider, reduce active defenses by the difference between 12 and the rider’s skill; e.g., someone with Riding-9 would have -3 to all active defenses.