May seem a silly questions but is there a way of forecasting when a cracking sunset will happen? Most evenings go by uneventful, but every so often you get a stunning sunset with vivid red and pink colours. I just wondered if there were any atmospheric conditions which help create these stunning displays. Any help much appreciated 

Certainly plenty of particles in the atmosphere is a key element. Some of the best sunsets appear during stagnant weather under high pressure with high levels of pollutants.

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I do find that the best sunrises occur when the sky is clear for hundreds of miles to the east, and I mean, properly clear over a long distance, but at the same time, a bank of medium level stratsocumulus associated with an advancing warm front is coming in from the west. When that happens, the sunlight beaming from the rising sun is able to undercut the cloud bank (even though the sun itself is still below the horizon) and the end result is something like this:
 


Note how the sun is still below the horizon but the underside of this quite high cloud base is already being lit up. At this point, the sunlight is cutting through the most atmosphere from a very, very low angle. I actually was able to tell this was coming an hour before the sun was due to rise so I got up, got changed, grabbed the camera and went down to the harbour and waited for it . . . and I proved to be right.
  The same can apply to the setting sun, but the sky needs to be clear for hundreds of miles to the west while at the same time the overhead medium-height cloud that is receding to the east is being lit up by undercutting sunlight.
  Low cloud such as stratus and cumulus aren't that good for showing up colours because the sun will already be above the horizon before they are lit up. Also, a clear sky is no good for picking out the colours because it's the clouds themselves that adds to the context - unless you like a hued colour type sunrise/sunset using just the clear sky alone.
   I guess pollutants can have an effect as it adds a red cast to it all, but it does show how the old adage "red sky in the morning, sailor's warning, red sky in the evening, global warming" does ring true.
  If anything, the best sunrises seem to occur during the more unsettled spells as alternating banks of cloud and clear skies sweep across the country and if it is timed just right with the sunset/rise then you'd get the money shot. Doesn't happen every time, though, of course.

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We're getting something very similar to the picture above now - a dramatic layer of orange-red alto-cumulus in the NW sky, looks stunning.

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Thanks for the response guys. I was hoping to get some good photos this evening as the clouds looked like they would provide a good sunset, however nothing too spectacular occurred. Are there any good prevailing conditions that guarantee a decent display or is it just luck?

That is indeed a very interesting question! As Ian has suggested for sunrises, fronts advancing from the west are a good indicator, and for sunsets, fronts clearing to the east. However, any situation where the sky at or just below the observer's horizon is clear will work, and there are non-frontal situations which can give that. Some are very difficult to forecast. Think about those random  banks of stratocumulus in winter that give the forecasters such a nightmare with regard to predicting frost.

I find the most interesting sunsets are where there is cloud overhead at multiple levels and the setting sun illuminates each level in turn. This can result in a spectacular sequence of shifting patterns, shadows and different colours over quite a long period, whereas a single level cloud bank can give spectacular results, but sometimes with only a single colour, and often very briefly.

Regarding location, you are better off near the coast, as the high concentration of salt particles suspended in the air over the oceans increase the amount of scattering out of sunlight the shorter wavelengths(violet and blue), giving sunsets a redder hue.

However, as well as being alert to the conditions, luck is a large part of it I'm afraid.

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Does anyone remember that spectacular sunset 4 years ago, after that Russian volcano erupted? It was early July, I think it was a Friday evening when it was really notable.

Also that afterglow during February 2008, that was bright.

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I saw the best sunsets when i was in china.  Funnily enough you very rarely see a blue sky - seems to be overcast with pollution.

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