But as we all know from our own lives, the experience of a new place/time isn't always coherent and understandable. Some sensory input leads to overload immediately (smell, sound, and pain-- notice how when we are overwhelmed with one of these, we close our eyes). Sometimes the different senses come in sequence-- we might be more audial and so figure out what we're hearing before we figure out what we're seeing.
Anyway, in a scene, we have to narrate the experience in a reader-comprehensible way. That might mean going back and forth between an inward experience ("she was overwhelmed by the din of the band,") and a more sequential and more mechanical chronological ("when she could hear again, she looked around and..."). But something that will help this feel more natural to the reader is to take care in switching between senses, with an action bridge easing the transit so that the experience is more than just an explosion of synesthesia (a confusion of the senses, so that the input doesn't result in the expected output, so you "feel" color and "smell" sound).
Here's an example of how -not- to do this, with several sensory experiences jammed in together without a transition--
His nose was assaulted by the garlic fragrance while a Joy Formidable song played loudly in the background. In the corner a black-and-white Snoopy dog lay chewing on a toy. Sunbeams streamed in through the open window.
There's no focus there, no connection, no experience. Whoever "he" is stops mattering as the sensory details just occur as if they are not being experienced by anyone, as if they're merely discrete occurrences. The reader is going to have a hard time assembling this into a place or experience. This is, btw, the sort of description that readers skip. They probably sense that it's just a pro forma description, dutifully put in there because scenes are supposed to have description.
So as you edit, consider rewriting such passages to actually create an experience. Some suggestions:
1. Think of this as a moment, a special moment. And choose it well. You don't have to describe the sensory experience of every moment-- that would be way boring-- so choose the moments you want the sensory to, if only momentarily, dominate. Have a purpose then for bringing in the sensory now, describing this moment.
2. The most important moment for the senses is at a shift in setting (when she leaves the hallway and enters the office, say, or goes outside), and when something in the setting changes, like another person enters it, or the tea kettle catches on fire. So whenever there's some change, particularly when the character moves from one setting into another, take a bit of time to describe the new experience. Many scenes will probably start then with a short unified paragraph about the new place. That sets the context for the reader, shows that there's been a change, and provides a way for the reader to experience the scene as if she's there. Describe the change, not just the setting.
3. Put it in someone's point of view. Really. This doesn't mean just sticking in the character name or pronoun (his nose). It means showing this character experiencing this. That means considering who this character is and describe what he'd notice-- as he notices it. If in fact he notices in a sort of scattershot way, all sorts of sensory input arriving at about the same moment, say so-- but make it important. Make it signify something about him or the moment he's in: The room was chaos. He couldn't breathe because of the garlic fumes; he couldn't hear anything over the pounding of the CD player. ... Most important, think of how he would experience it. Most of us have a dominant sense, and most experiences have a dominant "feel". What is that? If it's too loud for him to hear, that's likely to be predominant, so say that first maybe. If he's a musician, or loves or hates this band, he's going to have a different reaction than a tone-deaf Sinatra fan. Describe this person's experience, not a sort of generic set of sensory inputs.
4. Link the description to some danger or threat or awareness or emotion. The primary evolutionary reason we have most of our senses (especially smell) is to warn us of danger. Now of course every moment isn't dangerous, but our senses don't know that. Think of what in the scene needs to be noticed (again, especially when something changes-- we don't usually notice when they stay the same). If the picture of his mother on the wall is crooked... if a draft is coming in under the door... if the floor is gritty under his feet... those are things he probably couldn't help but notice and mentally remark.
5. You can have one sense dominate. That is, forget that about making sure all five senses are represented. That's mechanical and boring. Go into the experience and think about what it feels like. If she's leaving a dark movie theater and going out into a bright afternoon, for that moment, maybe the visual dominates. Talk about what the experience of dark to bright is like first. You can have her awareness expand as her eyes adjust, but thrusting in the lingering taste of popcorn at this moment will detract from the more primary sense.
6. What do you want it to MEAN? Do you want this to echo some emotion in the character? If she's angry, everything will be objectionable, including the lingering smell of her husband's aftershave. If he's feeling oppressed by a dream he had of his mother's funeral, the crooked portrait of her might amplify his sense of dread. If in fact the crooked painting is a clue that someone's been in the room searching for the papers he's hidden, show that awareness dawning in his head as he sees the painting. You can fill in the blanks around the meaningful bit, like she also angrily notices that the faucet is dripping again.
7. Think cause and effect. The sensory bit causes the character to do something, or he notices it as an effect of something he does. It's not just happening in some static between-worlds moment, but inside a scene where things are happening. Link it to action, maybe-- what he experiences as he moves through the scene or interacts with the setting. He notices that the floor is gritty because/as he walks over to the painting. Not every sensory bit has to be linked to action, but try that first. So he -stops in the doorway- and sees the room. He smells the garlic and waves it away with his hand, or goes to open the window. This will keep the scene moving, and the narrative focused on action.
8. Don't overdo it. Restricting yourself, say, to a paragraph of pure description might seem artificial, and feel free to break any self-set rule when appropriate. But having a guideline in mind will help you be selective about what you choose to describe. Everything isn't equally important, so decide what is important, and that's first and foremost going to be what is meaningful-- what reflects or causes emotion, what shows a change or threat, what he encounters as he moves through the scene.
9. Read writers who do this well and figure out what they're doing right. Too many writers think of sensory description as a chore-- I know I do-- and so do it perfunctorily to get it over with. But some writers use the sensory moments as a way to convey something in a new and interesting way. Analyze why you enjoyed this passage, how this writer focused, what the meaning was and how it was conveyed, how the language, sentencing, and paragraphing enhanced the passage.
10. If you're going to shift from one sense to another, try to make it graceful and organic. For example, group like-sensories together. In the first paragraph or series of sentences, group the visual. In the next, the audial. Find a way to unify. Also, find a way to mark the shift with a transition of some kind. Action here can help as a transition. He stops in the doorway to look at the room (visual). When he notices the crooked painting, he moves towards it and notices the grit under his feet (tactile). Or use a time marker to start the sentence of new input-- "When his ears stopped ringing (audial), he took a deep breath and for the first time noticed the faint tinny smell." The transition helps unify the different sensory bits, so they don't seem so willy-nilly.
If you're going to describe more than a couple sentences worth, consider a paragraph break when you shift from one sense to another. If that leaves you with a couple one-sentence paragraphs, well, deepen the experience. Say more about what he sees or what it means, so you have more than one sentence in that paragraph!
The problem, of course, is that we do experience sensory input willy-nilly. In real life, our bodies and brains sort it out immediately. But when we write, we don't have any way to convey that immediacy and totality. We're bound by the march of words down the page, the temporal limitation that only one word can happen at a time. We have to accept that limitation and make the experience as coherent and meaningful as possible within the restrictions of narrative and prose. And that does probably mean focusing on the character's experience, but parsing it so the accretion and sequence of input helps create the experience for the reader and adds to the meaning within the scene.
What are some other techniques you use to focus the description and make it understandable?