how to rotate an object smoothly

It says it in the title. I want to make the character turn right, left and backwards smoothly instead of instantly but with my script so far it looks glitchy for example when i jump and land but i was moving forward the player just plays the standing animation while moving instead of the run animation.
here is my script.

using UnityEngine;
using System.Collections;

public class Animation : MonoBehaviour {

	private MouseLook camera;
	public float time = 1f;
	public float speed = 1f;

	// Use this for initialization
	void Start () 
	{
		animation.Play("Standing");
		animation["StandToRun"].speed = 1f;
		animation["RunToStand"].speed = 1f;
		animation["Jump"].speed = 1.15f;
		Screen.lockCursor = true;
	}
	
	// Update is called once per frame
	void Update () 
	{
		if(Input.GetKeyDown(KeyCode.Escape))
		{
		 GameObject.Find("Player").GetComponent<MouseLook>().enabled = false;
		 GameObject.Find("Camera").GetComponent<MouseLook>().enabled = false;
		}

		if(Input.GetMouseButtonDown(0))
		{
	     Screen.lockCursor = true;
		 GameObject.Find("Player").GetComponent<MouseLook>().enabled = true;
		 GameObject.Find("Camera").GetComponent<MouseLook>().enabled = true;

		}

		print (transform.localEulerAngles.y);

		if(Input.GetKeyDown(KeyCode.W))
		{
			animation.CrossFade("Run");
		}
		if(Input.GetKeyUp(KeyCode.W))
		{
			animation.CrossFade("Standing");
			transform.Rotate(0,0,0);
		}
		if(Input.GetKeyDown(KeyCode.D))
		{
			animation.CrossFade("Run");
			transform.Rotate(0,90,0);
		}
		if(Input.GetKeyUp(KeyCode.D))
		{
			animation.CrossFade("Standing");
			transform.Rotate(0,270,0);
		}
		if(Input.GetKeyDown(KeyCode.A))
		{
			animation.CrossFade("Run");
			transform.Rotate(0,270,0);
		}
		if(Input.GetKeyUp(KeyCode.A))
		{
			animation.CrossFade("Standing");
			transform.Rotate(0,90,0);
		}   
 		if(Input.GetKeyDown(KeyCode.S))
		{
			animation.CrossFade("Run");
			transform.Rotate(0,180,0);
		}
		if(Input.GetKeyUp(KeyCode.S))
		{
			animation.CrossFade("Standing");
		    transform.Rotate(0,180,0);
		}


		if(Input.GetKeyDown(KeyCode.Space))
		{
			animation.CrossFade("Jump");
		}


	}
}

Try:

Transform.Rotate( Time.deltaTime * 10, 0, 0 );

That will rotate smoothly at 10 degrees per second around the x axis. Use Time.deltaTime multiplied by however many degrees you would like to turn per second.

Hope that helps

try this:

public float turnSpeed = 1.0f; //adjust this value to get a faster rotation speed.
float rotation;


if(Input.GetKeyDown (KeyCode.A))
{		
    rotation = Input.GetAxis ("Horizontal") * turnSpeed;
    transform.Rotate(transform.up, rotation);
}

for the D button its the same only it turns the other way since D is set up like that in the input manager.

for your S buttons you need to set them up manually in the input manager to actually use them the way you want to with this code.

also you can adjust the rotationSpeed inside each buttonpress “if” statement to get the desired rotation for each button you press.

hope this helps.