LSD,

The three keywords fields are in order of importance.  

essential keywords: the most important ones, what describes your subject straightly; only 50 characters to make it really relevant.
main keywords: other relevant keywords, synonyms; up to 300 characters.
comprehensive keywords: less relevant, broader terms

Have you read this?
http://www.alamy.com/stock-photography-keywording.asp

The main description goes in caption.  A more detailed description, sometimes with biological, historical or geographical information, goes in description.  

They have recently put zero relevance for description in the search tool, which is a good thing in a way.  For instance, I had a photo of a fortress and I added the description of the building, which has among other things a cloister, and a search for cloister returned my image, even if cloister was not in any keyword field.  

I find the relevance fields very smart.  They really help return a more valid search.  if someone looks for "lipstick", images with lipstick in the essential keywords will appear before those with lipstick in the main keywords.

Also Alamy takes into account the proximity of keywords. 

Use this keywording tool: http://www.findphotokeywords.com/

It can generate keywords in Alamy format.

It's on the right side.

I guess you can still choose and pick individual words in each box.

Thanks, I will try it out. It's not really the keyword itself that bugs me...its the splitting of them and deciding which ones go where. This may help.

Important words in the Essential, next most important in Main, third level and note, words that everyone looking at the image can see in the Comprehensive. The search looks for them with a ranked system, where the boxes are weighted accordingly. First word in the first box appears to be stronger than the last word in the same box and all words in all other boxes. Just look at it as a pyramid. By the way, title and location are searched along with everything else, at the lowest level. Description is now not searched.

It's good because you can make sure the most important words don't get lost in the rest of the words. You determine the future of your photos and can manage how they will show up.

Bravo Alamy, no categories!