How to reduce loading time between scenes?

Hello, I have a game in which I need to load the levels quickly, 1-5 seconds, but currently using Application.LoadLevel() the scene loads in 15-20 seconds. What are some tips to shorten the loading time?

Thanks!!

If you have Unity3d Pro you can use,

function Start () {
    var async : AsyncOperation = Application.LoadLevelAdditiveAsync ("Level name");
    yield async;
    Debug.Log ("Loading complete");
}

Loads levels much faster.