Ardumoto - Motor Driver Shield

hi there im trying to make two, two way motors work with a thumb stick.
and all i have is this and i cant seem to get is to work

int pin1 = 0;
int pin2 = 0;
int pwm_a = 3; //PWM control for motor outputs 1 and 2 is on digital pin 3
int pwm_b = 11; //PWM control for motor outputs 3 and 4 is on digital pin 11
int dir_a = 12; //direction control for motor outputs 1 and 2 is on digital pin 12
int dir_b = 13; //direction control for motor outputs 3 and 4 is on digital pin 13

void setup()
{
pinMode(pwm_a, OUTPUT); //Set control pins to be outputs
pinMode(pwm_b, OUTPUT);
pinMode(dir_a, OUTPUT);
pinMode(dir_b, OUTPUT);

analogWrite(pwm_a, 100); //set both motors to run at (100/255 = 39)% duty cycle (slow)
analogWrite(pwm_b, 100);

}

void loop()
{
digitalWrite(dir_a, LOW); //Set motor direction, 1 low, 2 high
digitalWrite(dir_b, LOW); //Set motor direction, 3 high, 4 low

delay(1000);

analogWrite(pwm_a, 255); //set both motors to run at 100% duty cycle (fast)
analogWrite(pwm_b, 255);

delay(1000);

digitalWrite(dir_a, HIGH); //Reverse motor direction, 1 high, 2 low
digitalWrite(dir_b, HIGH); //Reverse motor direction, 3 low, 4 high

delay(1000);

analogWrite(pwm_a, 100); //set both motors to run at (100/255 = 39)% duty cycle
analogWrite(pwm_b, 100);

delay(1000);
}

" i cant seem to get is to work" does not say what does not work. Do the motors not turn at all? Or do they turn to fast/wrong way or what?

Your subject mentions "Motor shield". How have you verified that the wiring is correct? - perhaps including a schematic here might help resolve the problem.