Smells and the description of odours can be used to good effect in fiction writing and similarly to sound, can invoke a wide range of emotions. The smell of fresh bread baking can invoke childhood memories of a much-loved grandparent, or it can emphasise that the character is in a supermarket.
As writers we arguably underestimate the usefulness of the description of smell. A well-used description can place ideas into the reader’s mind, effectively creating so many blanks for the reader’s mind to fill in. For me the term “fresh-cut grass”, just three words long, invokes spring. My mind will fill in the rest: sun shining, cool breeze, flowers blooming, bees, lazy sunday afternoons in the garden sipping my drink of choice.
Similarly to my example of a baby crying in the post about sound, smell can be used to dramatic effect. The most obvious is a fire which we’ll smell long before we see it.
Horror writers are highly likely to use smell as a plot device: the smell of rotting or burning flesh can build apprehension. Stephen King refers to the resurrected animals in Pet Sematary smelling of soil and rotten flesh and I can recall several of James Herbert’s novels referring to a certain smell (such as roses) preceding a supernatural event.
I can think of precious few examples of fiction where taste has been used to particularly good effect. In fact I can’t think of any. It is probably because its range is so limited, after all we associate it almost entirely with food and it isn’t very often we read a detailed description of somebody eating a meal. In the real world, most of us do that three times per day and as adults we rarely eat things that we find unpleasant.
There are other uses. Writers often in their text refer to air ‘having a bad taste’, which usually means that oxygen supply is limited. Though technically they probably mean ‘smell’, some smells are so pungent that when breathing in through the mouth they do leave an unpleasant taste. A character deciding to put a gun in his mouth might notice the taste of oil.