Dust Form, and other spells/effects granting incorporeal form.
"An incorporeal creature moves silently and cannot be heard with Perception checks if it doesn’t wish to be. It has no Strength score, so its Dexterity modifier applies to its melee attacks, ranged attacks, and CMB. Nonvisual senses, such as scent and blindsight, are either ineffective or only partly effective with regard to incorporeal creatures."
If you want to be really sneaky, just ditch your physical body.
Teleport works too
