94 Overdrive. When to use?

Hi,
I got a 94 4x4 XL a few months ago and I have a question regardin the OD. (Fist car that I have that has it, all others where 5speed)
When do I drive in OD?

Thanks....

i usually keep my vehicle out of overdrive in town, i here the tranny lasts longer, and you don't have to wait for the tranny to shift out of it,

then as soon as i exit the town i put it in overdrive, unless i'm pulling a trailer