Is to best to optimize for singular words? Example: Chiropractor Tool vs. Chiropractors Tools Does "Chiropractor Tool" fulfill both keywords since its a "core" keyword. ?
Usually the singular form of a keyword gets more searches. That might not be true for some industries though. You would need links with both anchor texts. The search engines won't give you credit for both the singular and plural. They used to work this way, but I guess singular and plural can be different niches for some keywords. Yahoo might still give you credit for both singular and plural, but I am not positive.
UseGoogle Adwords Keyword Tool. Check which phrase has little advertiser competition and a large volume of searches. It works with me.
The advertiser competition listed in the Google keyword tool has little to do with organic search competition. That is referring to how many people are bidding on that keyword using PPC.
Try with the keyword tool included in the WebCEO software (free)...it analizes the number of searches (your potential visitors) vs. the number of sites (your competition)...maybe you can get your answer there
Reun it thru Adwords Keyword tool first, but I go by the rule of thumb that the first word (Chiropractor) will be singular and the last will become the plural. Then go with the largest number of searches.
A lot of times it makes sense to optimize for the plurals. You can then capture traffic for both words. Most of the time the plurals will be less competitive allowing you to rank more easily.
You'd better put 2 or 3 words, you get less visitors but normally convert well. One word is really competitive now..
It all depends and what you want, if you want a less competitive search term usually the plural phrases are good, it is easier to rank higher on them