First off, I'd steer you towards Dragonsfoot. They have a very active 1E forum and you'll get a blizzard of answers in a hurry, I'm sure.

The 1E DMG p. 69 discusses figures in battle, where both grid and hex based systems are viable. Gary suggests using 1" per face hexes/grids for 25mm figures.

The PHB gives movement rates. In tactical combat situations, usually 1" = 10 feet of movement per round (minute). So a 12" move = 120 feet. When charging indoors, speed is doubled. When charging outdoors, you get a +33% modifier (+50% if you're a quadraped) (DMG 66).

I believe normal movement outdoors is at 3x speed, although I usually treat all combat at the 1" = 10 feet rate (just my personal house rule). Note that all missile fire ranges are triple outdoors (10" range = 100 yards outdoors, 100 feet indoors).

ncG1vNJzZmivp6x7prrWqKmlnF6kv6h706GpnpmUqHxyv9NmnJ1lmJq5sXnWoquhZZ2kw6a5xKerZqqlobK0epFpaW9sZWQ%3D