It can occasionally be fun to employ random encounters but such encounters often feel entirely "forced", not least because frequently running into monsters outside of an apocalypse makes one wonder how the local farmers survive without at least a ring of wardstones surrounding their hamlets. At least those who can't help but wonder how various game elements should impact on the surrounding societies. But you don't want to brush over every travel journey nor do you want to simply populate it with mundane sights (though you can do so).
Perhaps when you first roll to see whether an encounter happens, you then rolled a 1d6 to determine how many days (or hours, depending on the frequency) between when the characters first get an inkling of it and when they first encounter it. If you get, say, a three on the 1d6 you pick which of the following foreshadowing elements you would like to use before they encounter the creature itself.
Signs of Feeding
Sighting of the Creature
Threatened by the Creature (or see warnings left behind).
Naturally the way these elements would manifest may differ depending on the creature encounter. A mohrg will leave different signs to a dire bear or a vampire, after all. One might come across a damaged cart with an irritable farmer who hid when the bear slammed into it or spot the farmer dead and laid out across the back of the cart with his throat ripped out. Tracks might be left by feet, tentacles or stalks bent by a heavy wind.
What do you think? Do you ever make a point to really foreshadow your random monsters?