I've never felt I've really understood the 'Hard Problem' of consciousness. Although not a new problem, David Chalmers seems to be the contemporary go-to source. Here he is in 1995 with 'Facing Up to the Problem of Consciousness':
"It is undeniable that some organisms are subjects of experience. But the question of how it is that these systems are subjects of experience is perplexing. Why is it that when our cognitive systems engage in visual and auditory information-processing, we have visual or auditory experience: the quality of deep blue, the sensation of middle C? How can we explain why there is something it is like to entertain a mental image, or to experience an emotion? It is widely agreed that experience arises from a physical basis, but we have no good explanation of why and how it so arises. Why should physical processing give rise to a rich inner life at all? It seems objectively unreasonable that it should, and yet it does." [my italics in there]

It seems to me all this distils down this to two short questions:
• Why do we have consciousness?
• How can we have consciousness?

Why Consciousness?
Consider that consciousness contains mental models of the world and its phenomena. Not a single, complete or accurate models certainly, but without doubt this still is a very adaptive feature. As humans have flourished via co-operative activity it’s not hard see the value of making abbreviated mental models we can transmit easily to others. Harvesting blackberries together we might discuss the ideal quality of that deep blue we know means a great pie will had at the end of the day. We'll probably share a good mental image of the topography of the area – discuss foraging directions, maybe even externalize this image with a little mud-map. That curious sensation of middle C is a usually rattlesnake around here, so best share that between our mental models as well. The day passes. When blissfully pondering all this I feel a twinge of anxiety as you catch me standing about savouring blackberries. You never do like me to leave you with all the work whilst I go about philosophizing - usually you punch me in the arm. Some internal realities are quickly updated to my mental model – with both your experienced emotions and mine - present, past and future. As the day progresses our similar but unique mental models constantly update as our external and internal conditions change and flow.

How Consciousness?
So, just in this, we have an everyday example of consciousness showing some pretty obvious functions at work. Familiar, but I doubt it’s a simple thing below the surface. In the pursuit of a piece of pie doubtless a great deal of complex brain activity went on. Had dragging about meters of cable through the brambles seemed more practical, I'm sure at least crude correlations of increased EEG brain activity could have been seen varying with demands of consciousness.

I think the workings of the material world is sufficient to account for this phenomenon (Physicalism is it?). While it's obviously too crude to say 'the mind is the brain' - it seems reasonable to propose the mind is at least 'a function of the brain'.

Patricia Smith Churchland derided mind-brain correlations such as Roger Penrose's theories, saying that "Pixie dust in the synapses is about as explanatorily powerful as quantum coherence in the microtubules." (Brain-wise: studies in neurophilosophy, 2002). I suspect this conflates ‘material substance’ with ‘material function’. We know very well of one way to model the world using tightly organised flows of energy through matter. We call this computing. Let me stress here that I’m not saying that the mechanics producing consciousness are just the same as for computing. But we at least know that very complex world-modelling occurs sans the pixie dust. Sure, it would be very nice to know exactly the minutest brain mechanisms involved. And I expect we will do, down the track, but even Darwin was not wrong until the discovery of genes.

To my mind what's more perplexing is the how of subjectivity. How can a thing be conscious of itself? Is there a little man in our heads who monitors our sensations and feelings? If so, who is conscious of this monitoring - another little man? That’s an oldie but a goodie, and I can't quite remember the author of this reductio (I think it was a reply to Descartes’s ‘ghost in the machine’, does anyone else know?). In any case, Nagel sparked concerns like again these back in during the Hard Problem's revival from the 1970s.
"If physicalism is to be defended, the phenomenological features must themselves be given a physical account .." (OK, we've covered some of that ground but we’ll return to it)
"... But when we examine their subjective character it seems that such a result is impossible. The reason is that every subjective phenomenon is essentially connected with a single point of view, and it seems inevitable that an objective, physical theory will abandon that point of view." ("What is it like to be a bat?" 1974).

Herein lies a questionable assumption: That consciousness consists of "a single point of view". In reality internal experience is often quite conflicted, and we are in least two minds about everything from a menu preference to ideas of jurisprudence. Despite what we say, we often aren't even fully aware of how we feel about things until our emotional responses to events interact over time with our thoughts about them. Personally I don't hold much faith in Freud, but one thing he got right is that a mental persona consists of far more than a "single point of view".

Physiologically that really shouldn't surprise us. Almost our entire brain is bifurcated and duplicated, not to mention subdivided into a complex web of many smaller structures all in continual inter-communication. Often these are working on different aspects of the same task – ‘parallel processing’ if you like. We don't need call upon an infinite series of observers to account for the subjective experience when just such a hall of mirrors would suffice: The inner life of self-consciousness may consist of one brain region of the interrogating another for results, then this process reversing and repeating towards resolution. Of course, when asked for if we want that second slice of pie we have to quickly gloss over this process and present a single view. The ‘single point of view’ is a necessary fiction, but a fiction nevertheless (here I think, is an interesting intersection with theories of personal identity)

Who is not familiar with subjective phenomena of an 'internal monologue'? Well, that's a question I'd love to see investigated. It might be very fruitful research to compare the reports of the internal monologue of people with very different brain anatomies, especially those with only one hemisphere (yes, surprisingly they can often function quite well) or those with a severed corpus callosum (that pencil-thin connective nerve bundle between the hemispheres).

Say no to Philosophical Zombies:
All this relates back to the 'why' question. If there was none of this inner modelling and updating then perhaps we wouldn't have or need any subjective experiences. We probably could get by as philosophical zombies - the kind of stimulus-response automata that B.F Skinner thought his lab rats were. (David Chalmers also came up with this image).

But being in two minds about things, while unfashionably indecisive, is very adaptive indeed:

First, playing out various consequences in a mental model hurts a whole lot less than relying on continual trial and error.

Second, we can also play out our own conflicting motivational processes in the relative safety of our own skulls - checking and balancing these against one another before acting in the world.

Third, we can model that vital element of human social reality – ‘other minds’. Thinking about how things effect other people's reactions is a vital faculty. Even better is to empathise with another. Doing this is almost to run their software on your own hardware. In the complexity of the human social world this seems far more adaptive than just running the basic zombie algorithm.

I'm sure there are many aspects to the Hard Problem I've overlooked. This is my first post. It’s blueberry pie I seek, not the humble stuff.