Taxonomy of keywords question

I don’t use plurals for agencies but I do for my sym site where appropriate

I use 2 or 3 categories at most — for a rock texture, geological detail, etc, I may not put it in say Zion National park but would just add it to textures

http://cascoly.com/symbio/list.asp?list=42 shows how many categories each site has, and average number of images per category

Regarding phrases, I typically use them to avoid spam that you’d get if you made the keywords individual words.

For example, with this image I used the phrases Codz Poop and Palace of the Masks as well as the word masks. If i were searching for just palace, I wouldn’t want to see this, but just masks would be OK. Likewise, I can’t put poop as a single keyword (think pooh in UK English versus US English).

Similarly, there’s no apache in this image, so I used apache trail as a phrase, but also trail individually in case someone doesn’t care which trail.

I try to balance covering all the buyer search possibilities with keeping thing spam free, and generally try to remember plurals where appropriate