First of all. It is very hard to predict a great sunset/sundown. But you can indicate whether its goint to be a good or a bad one.
Time of sunset/sunrise
The basic is that you know what time the sun is going to set or rise and with which azimuth. Google will help you finding it easily. Personally I use this website hemel.waarnemen.com/applets/op…
It only works in the Netherlands and Belgium, but I am sure there are also sites for a lot other countries (www.sunrisesunset.com/custom_s…. It not only gives the times and azimuths, but also the time twilight is getting started. If you cant find this information you can say it is approximately 45mins-1hour before/after sunrise/sunset. The time of twilight is also known as the Golden Hour because then the sky will look at its best. So dont leave the beach or the hill or whatever you are standing on when the sun isnt visible anymore. The best might be yet to come.
Predicting the beauty of the sunset/sunrise
This is way harder then look up the time of the scene. This requires training and dedication. But there are a few things that can help.
As long as the sky is not plain grey, and you can see a little contrast between the clouds there is a chance on a great sunset/sundown.
When there are zero clouds in the sky, but you can see some clouds at the horizon there is a change on a great sunset. Sometimes the clouds arent visible with the eye, but they can be visible using your sunglasses. If you cant see any clouds because of buildings etc. lines made by airplanes might be useful. If they arent plain white, but slightly red/orange/pink the chance on a great sunsets is significant greater.
Look at the weather forecast. If the weatherman is speaking about high clouds (cirrus or strato-cumulus) youd better have your batteries charged. The chance on a super sunset is at its best!
As said in #1: as long as the sky doesnt look plain grey there is a chance on a great sunset. Grey days can even give great sunsets with wonderful red stripes at the horizon, but it only last a few minutes:
A nautical saying is: "Red in morning, sailors take warning, red at night, sailors' delight.". You can turn that around: Look for red skies at sunrise before a storm and at sunset after a storm. I am not sure if this works around whole the globe.
Particles in the atmosphere can cause great colours during sunset sunrise. When there is forest smoke somewhere on your continent it might help. It depends on the locations. As it is in the west, it affects the sunrise, if its in the east, it has a positive effect on the sunset. The same for volcanic eruptions and Sahara sand. This has a positive effect for a longer period.
Have a look at satellite shots from your area. They are not always as useful as youd want to, but it can help. Use Google Earth for example. It gives understanding in the clouds that are coming.
When you wake up in the early morning and the sky is still dark its sometimes hard to see if the sunrise is going to be great. And nothing is as frustrating as waking up early for nothing. When you wake op look out your window with no lights on. You might be able to distinguish some clouds or see a star. It might indicate you didnt wake up for nothing.
Keep in mind that a sunset/sunrise is a beautiful phenomenon because it cannot be predicted by standard rules. Keep looking to the sky and try to get to read the information its giving. Believe me, you can get better in it.
Smog can create great effects, but it also can mess up the sunset/sunrise. If you are IN the smog it has a positive effect, but when you look from a clean area up to a area full of smog it can have the same effect as low clouds and it can make the colours at the horizon look dull. For example: I live in the Netherlands and when I look out of the coast from some places, I can see a lot of smog from Belgium. Not exactly perfect for sunsets.
Smog is mostly useful during the summer.
I havent found a smog index yet, but if you know one, please note me!
The best sunsets/sunrise are most of the time in one part of the year. It depends on where you live (continental scale). You might know what this period is by experience.
If tomorrow is going to be warmer then today then chances are there will be a reddish or even red sky at sunset.
Clear skies can also give nice sunsets, but then you need to have it from the late afterglow
I hope this information was useful to you. If you have other tips. Let me know them please. Good luck with your sunset/sunrise photography.
PS. I am not a meteorologist, but just a 17 years old who is still in high school with a passion for photography. This information is gathered by browsing the internet and for the biggest part personal experience. Of course there is another factor for shooting great sunsets/sunrises, and that is time. You need to have the time to go out and shoot. I think thats the most frustrating part of it all. You can reduce this frustration by taking your camera everywhere with you.