CharacterController.SimpleMove

Description

Moves the character with speed.

Velocity along the y-axis is ignored. Speed is in units/s. Gravity is automatically applied. Returns if the character is grounded. It is recommended that you make only one call to Move or SimpleMove per frame.

using UnityEngine;
using System.Collections;

[RequireComponent(typeof(CharacterController))]
public class ExampleClass : MonoBehaviour
{
    public float speed = 3.0F;
    public float rotateSpeed = 3.0F;

    void Update()
    {
        CharacterController controller = GetComponent<CharacterController>();

        // Rotate around y - axis
        transform.Rotate(0, Input.GetAxis("Horizontal") * rotateSpeed, 0);

        // Move forward / backward
        Vector3 forward = transform.TransformDirection(Vector3.forward);
        float curSpeed = speed * Input.GetAxis("Vertical");
        controller.SimpleMove(forward * curSpeed);
    }
}