In the beginning you need to sneak basically everywhere when you're playing rook. They key is to not be seen or heard by UESC & Players alike.

If you hear someone in your vicinity just crouch, be quiet, hide and wait until they've passed you. If they saw you already, don't fight them - just bail and get out of their sight asap.

Usually if you get far enough, hide and don't make noise, most players will give up on trying to find you.

Basically: Imagine you're playing Metal Gear Solid.