long currentTimeInMs = clock.getTime(); // whatever the timer is called

GamePadState gamepadstate = GamePad.GetState(PlayerIndex.One);
float RightTriggerValue = gamepadstate.Triggers.Right;

// wait at least 1second(=1000 ms) until you can shoot again
if ((lastTriggerTime+1000)<currentTimeInMs && RightTriggerValue == 1)
{
   Shoot();
  lastTriggerTime = currentTimeInMs ; // lastTriggerTime is a member variable or some other kind of "global" state 
}

Or another option (to strictly fire once per trigger pull):

Keep two GamePadStates, "current" and "previous".

Every frame, push current to previous, and then update current from GamePad.GetState().

previousState = currentState;

currentState = GamePad.GetState(PlayerIndex.One);

Then only shoot if the trigger is "freshly" pulled, but not if it's being held down.

float currentRightTriggerValue = currentState.Triggers.Right;

float previousRightTriggerValue = previousState.Triggers.Right;

if(currentRightTriggerValue == 1 && previousRightTriggerValue == 0)

{

Shoot();

}

I've found that creating an inputManager to do comparison checks like these for any button is IMMENSELY helpful. Then this whole mess can be wrapped in a method call like

if(inputManager.IsTriggerJustPulled(Triggers.Right))

{

Shoot();

}