I tend to shoot for above -6dBfs peak on percussive and transient sources. I shoot for -14dBfs on average with smoother or more compressed signals, and never allow myself to hit 0dBfs. If you hit 0dBfs on the way in, you've clipped it, period...whether or not you want that sound is up to you. Depending on your preamp and microphone, you could very well distort in the analog domain long before you trip the red clip indicator in Pro Tools... There really is no valid reason for recording "as hot as possible" with 24 bit converters unless the distortion usually present when doing so is key to your production.