The "search phrases" versus "single words" discussion is still going on:
I've asked people who wrote the blooming standard for HTML and they
don't know. They all can handle comma, space or just a space between
words. However, if you set off ANY phrase with a comma, you have to
separate ALL the words with commas too.
Phrases (two or more words) need an EXACT match. Single words don't.
If your phrases don't match what I enter, I won't see your site.
I have had the best AVERAGE luck with just a string of keywords,
leaving it up to the search engines to match them with the text the
user typed in.
Start with the most common nouns that describe the product - always
include the words your customers use even if it's not the technically
correct word. Then add the critical adjectives and adverbs that are used
to describe the product. And the common ways to misspell the words.
Example - I'm selling a gadget that cuts and cooks potatos:
"french fries fry frys fried potato potatoes potatos maker cutter fryer
cooker deep cooking making cutting"
That matches, in 16 words, nearly every way someone would look for the
french fry cooker
french fried potatos/es
French fry cutter
making french fries
cooking fried potatoes
potato cutter for french fries
french fry cutter