Good idea is just to experiment - try to use different exposures and then look, when your pictures are best.
As mdebono said - sometimes you might be not able to judge wheter the exposure is correct basing only on LCD display. For example it the sunny day it might be difficult to see it on LCD - it's not enough bright. But you'll see histogram at least and it can help you:)
BTW - remember, that CHDK histogram is based on LCD live view. And camera creates live view basing on settings you have set - shutter speed, aperture and ISO. If you use CHDK overrides, then camera don't know about that until it get shot, so live view will be not acurate. According to this - CHDK histogram will be not very usefull in that cases.