By no means an exhaustive list, just some things that come to mind.

Do:

• Save a preset every time you feel like you're getting somewhere. All it takes is one mis-adjusted sculpt to ruin a face
• Remember that you can always back out of a sculpt with Esc/Tab, if you feel like the adjustments are going to ruin things
• Use "player.setscale 1.05" (or so) to get a better look at your character's chin/neck (default is 1)
• Use "fov 40" or even lower to zoom in on your character's face (use "fov" by itself to revert to default)
• Use the Fine sculpts if you only need small adjustments, and remember they're there if you need just a bit more scaling/rotation out of one of the main sculpts
• Remember that rotating and scaling certain bones can effectively change the shape of parts of the face (notably Dimples, Chin and Cheekbones)
• Build your face in moderate light. Perfect lighting makes a face look nice, but you don't want your face to ONLY look perfect in perfect lighting. Moderate lighting at an angle will highlight problem areas like mismatched levels between bones (causing lines/dropoffs in the facial skin)
  

• Go an hour without saving a preset. Seriously, it takes 10 seconds
• Scale a part all the way down as far as you can, unless you know what you're doing
• Forget to check your face at multiple angles; perfection looking at it straight-on is cool and all, but you're probably going to regret not checking the face in profile when the first cutscene hits you
• Use the plastic surgery menu. This disables FOV adjustments, can set some wonky lighting, forces a "happy" expression, and costs money. Find some decent lighting, face your character just to the side of it, and use "showlooksmenu 14" from the console