I know most of the local roads that are good to cycle on, so most of the time I've already got a route in mind when I set off.
I rarely go west, as that's into the city and don't often head south as that's down into the Aire Valley which means a long drag of a climb back home on a limited number of busier routes.
So most routes tend to be north, northwest or to the East.
Wind direction and strength also plays a part, although it's generally from the west so heading east (most of my routes) means it's a headwind on the way back.

I do intend to explore a bit more next year though, time permitting.