As you create your characters, whatever your ultimate purpose in doing so might be, it’s likely they’re going to have an emotional response to something sooner or later. Unless they are coming into contact with our world from an entirely alien, outside perspective (which in and of itself can make for a good story), they’re going to experience emotions the way human beings do. As you consider this, also consider the fact that no emotion exists in a vacuum.
Unless you’re spiralling alone through the void of space.
What I mean is, our emotions come from somewhere. Our psyches, histories and experiences shape the way we react to things, and act on those reaction. A middle-management office worker is going to react to a corpse differently from a battle-hardened veteran. A schoolteacher’s going to take comfort in different things than a member of a biker gang – lets say she likes kittens. It’s important to keep in mind where the character’s been, how they’ve been raised and what brought them to their current state of being when you set out to describe a scene in which they need to feel something – which is most of them.
Now, there are always exceptions. The middle-management officer worker might *be* a battle-hardened veteran. A hardcore biker might have no problem whatsoever finding the sight of week-old kittens adorable and decorating his home or even his bike in such a motif. These characters may lend themselves to be more interesting than those who have only a single mode of existence or thought, but don’t discount those ‘simple’ characters as being uninteresting or dull. As long as they speak, feel and think like human beings (or whatever their species happens to be), they can be interesting.
A great and recent example of characters showing emotion, and establishing those feelings in a short period of time, is Chuck Wendig’s Irregular Creatures. Seriously, read it again, and watch how the characters feel, grow and change. Take in how they react to the weird stuff that happens. Put yourself in their shoes, which Chuck’s writing makes very easy.
What? You don’t have it yet?
Well, lucky you. It’s on sale.
Go get it.