This is how I keyword...
Key wording can be very intimidating...you sit, you think and wonder what to type and when you have typed all the words you can possible think about you still have only scratched the surface of what the image is all about.
You try and think what a possible buyer might type when looking for an image...but then...you don't know what they are looking for so how could you know what to use as a title or description.
When I keyword I tend to use a few simple questions.
Where...where is this image taking place and is that relevant?
What...what is happening in the image?
Who...who is in the image?
When...when is the image taken if relevant to the image?
After I have used these questions to think out keywords I usually have quite a descriptive list. From there you can let your mind wonder to the less relevant to the image, being careful not to spam or use incorrect keywords.
Just a note on how I make my keywording a little easier.
Have a super weekend all
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Relevant related image searches
Photo credits: Michael De Nysschen.