Early game tip for SoC, though I assume it works for the others: Avoid overloading yourself on return trips to sell junk. Instead dump everything onto a dead body and drag it back to the store. Doesn't matter how much is on it, you drag it at the same pace, which is very very slowly, but a good haul can more than make up for the time spent and is a hell of a lot less bothersome than running back and forth carrying small loads on yourself.
It's been ages since I last played it, but I think there's an auto run button. Walk in the general direction of a store along the main road then alt tab out and do other shit while you pay attention to the in game sounds. The pack of dogs near the starting town can sometimes aggro you if you wander off the road.