I usually shoot in RAW, so that allows me to pick the exact white balance for the shot. But when I shoot the shot I still like to have the White balance as close as possible becuase that will effect the preview image imbedded with the RAW file and seen on the LCD screen. Each dSLR is different for setting custom white balance. On my Canon 20D, I shoot a reference shot of a gray or white card and then I set that as the reference for CWB and then set the camera to the Custom White Balance mode. The white balance will now be right on. If I'm in a hurry and the above isn't practical, then I set the camera to the K mode for WB (Kelvin settings) and use 5700K which usually gives a nice balance for daylight shooting.
If using fill flash or a reflector, the key is to make sure you get a catchlight in the eye.
Experiment with different settings to see which gives the best catch light. If all else fails, add the catch light in photoshop.