Servo not working in arduino

Hi guys,
I bought this servo:http://www.robosoftsystems.co.in/roboshop/vts-08b.html and connected an external power supply and used this code

#include <Servo.h>

Servo myservo; // create servo object to control a servo

void setup()
{
myservo.attach(9,600,2400); // attaches the servo on pin 9 to the servo object
}

void loop()
{

myservo.write(15); // sets the servo position according to the scaled value
delay(2000);
myservo.write(0);

// waits for the servo to get there
}
I have adjusted the delay from 15 to 2000. It doesnt work. I have also used an external power supply to power the servo. What am I doing wrong?

How your servo should be wired and simple servo test code.

// zoomkat 10-22-11 serial servo test
// type servo position 0 to 180 in serial monitor
// or for writeMicroseconds, use a value like 1500
// for IDE 0022 and later
// Powering a servo from the arduino usually *DOES NOT WORK*.

String readString;
#include <Servo.h> 
Servo myservo;  // create servo object to control a servo 

void setup() {
  Serial.begin(9600);
  myservo.writeMicroseconds(1500); //set initial servo position if desired
  myservo.attach(7);  //the pin for the servo control 
  Serial.println("servo-test-22-dual-input"); // so I can keep track of what is loaded
}

void loop() {
  while (Serial.available()) {
    char c = Serial.read();  //gets one byte from serial buffer
    readString += c; //makes the string readString
    delay(2);  //slow looping to allow buffer to fill with next character
  }

  if (readString.length() >0) {
    Serial.println(readString);  //so you can see the captured string 
    int n = readString.toInt();  //convert readString into a number

    // auto select appropriate value, copied from someone elses code.
    if(n >= 500)
    {
      Serial.print("writing Microseconds: ");
      Serial.println(n);
      myservo.writeMicroseconds(n);
    }
    else
    {   
      Serial.print("writing Angle: ");
      Serial.println(n);
      myservo.write(n);
    }

    readString=""; //empty for next input
  } 
}

The code that I pasted is simplest in its form . I dont need any user input. All I need is for the servo to move which does not appear to be happening. I have wired up the circuit in the same way. Any ideas?

. It doesnt work.

What does it do?

It just sits there without moving. No rotation.

Is it connected to the right pin?

Okay. I finally figured it out. The issue was I had not connected the ground of the arduino to the ground of my power supply. It works fine now.