Adding In The Playerprefs To Save Simple Information

Hello community,
On my first game I am now trying to add PlayerPrefs so that the player’s health and score can be saved until the end of the game. This will eventually lead to a leaderboard but for now I am just trying to get everything to work so I can call it in later on my loadlevel and endgame scripts. The player gains score by killing enemies and bases, picking up health and losing score by being hit with enemy bullets. This is my script for player counters with health and score. 1st question: Is what I have done already with playerHealth correct? 2nd question: If not, what did I do wrong?

static var playerHealth = 10;
PlayerPrefs.SetFloat("Health", playerHealth);
static var playerScore = 0;
function Start () 
{
playerHealth = PlayerPrefs.GetFloat("Health");  // makes sure player has same health from last level or 
}

function Update () 
{
//if(playerHealth <= 0)
//{
//Application.LoadLevel("Game Over");
//}
}
 function OnCollisionEnter (collision : Collision)
 {
 if (collision.transform.name == ("Missile(Clone)") && playerHealth > 0)
 {
 playerHealth -= 1;
 playerScore -= 10;
 }
 else if (collision.transform.name == ("Bullet(Clone)") && playerHealth > 0)
 {
 playerHealth -= 1;
 playerScore -= 5;
 }
}

The way i did it for my scoring and general level checking … stuff, was to make a governor game object and used a DontDestoyOnLoad command on it. I check with a camera script if the object is in the scene, and if it’s not, load it. So i keep stuff in that as it goes on through the scenes unchanged, and when the user is done playing i’m saving in playerprefs.
For the health check, i’d put it in the “do damage” function of the enemy. To trigger a check when the enemy hits instead of on every frame. (Or in your case, in the collision check you have for bullets and missiles.)