As writers, we are told repeatedly to use all five senses to convey setting. Although most readers wouldn't even notice, the presence of all five senses helps engage them and make them feel more part of the action.
By far the most common sense used in scene setting 'descriptions' is sight. Visualisation happens first -- colour, form, size -- and from visual descriptions, most readers can imagine what a scene looks like, and some can even 'play' the scene in their head like a movie in the mind.
But what about the other senses -- hearing, touch, smell and taste? Hearing is the next easiest to use, I think. It's relatively easy to throw in some birds chirping, or a baby crying, or people laughing etc. Touch too is fairly straightforward; you can use temperature, texture, hardness/softness etc to add dimension. With both these senses, the challenge is not to use the same sounds and textures repeatedly, and to instead ensure that they are specific and original (unlike my examples!).
Which brings me to smell and taste -- the most difficult in my view. Not only are they challenging to call up (for reasons I'll come to in a moment), but they are challenging to implement subtly and successfully. It's very easy for the use of these senses to appear self-conscious in narrative. I've read novels where the author seems to be working through a checklist: have I used sight? (of course, yawn); any sounds? (too easy); what about touch? (yep), smell? (check!), taste? (I'm working on it . . .).
So why is it so difficult? Here is a theory I came up with recently. I think the reason is that our senses of smell and taste (aside from when we're eating) are simply not used as often. I suppose it could just be me, but I don't actually use smell or taste much to engage with my surroundings. Most of the time I don't smell or taste anything at all.
I experimented with this as I walked home last night. I focused on smelling my surroundings. And most of the time I didn't smell anything. My sight and hearing never ceased (the latter despite the music blaring from headphones), but most of the time I smelt nothing. It was only when I walked through a cloud of scent left by a passing woman, or I encountered a jasmine bush or an open garbage bin, that I smelt anything good or bad.
Consequently I now believe that smell (and taste) should be used as an 'accent' sense, to be deployed strategically in narrative for maximum impact. For isn't that the wonderful thing about brushing against a mint or rosemary bush? The scent smacks you in the face. And while I'm not advocating that the use of smells or tastes should stand out in narrative, their power should perhaps be reserved for the scenes where added setting impact is warranted, for they sure do pack a punch.