There is one thing that I have not seen anybody mention: The day VFR minimums in Class G airspace are 1 mile and clear of clouds. It is fairly straight-forward to estimate visibility by knowing your runway length, and observing how far down the runway you can see. If you can see the end of a runway that is a mile or more in length, you are legal to go. It is somewhat harder with shorter runways, especially if there are trees off the end, but it is a yardstick to use.

Joe