You really need to take into consideration the keyword "trigger" then worry about the actual ranking websites. Since Googles most recent updates panda and penguin they have focused on a few more underlying factors such as displaying the appropriate amount of pages for a particular keyword, as well as what types of sites they are displaying (as if there wasn't enough already) when delivering quality search results. This has always been in their practice but I think it is more apparent today. What I am talking about is; when people are typing a specific keyword/phrase into Google the are looking for something pertaining to what the keyword "IS". Here are some examples:
If you type in something like: Running Shoes
This will turn up a number of different results because it is such a broad term. The search engine user can be looking for pictures of running shoes, online stores, local stores to buy running shoes, and maybe some reviews. This term is broad so it is going to have "mixed" search results. Now you have to ask your self a few questions;
1. What is my site aimed/targeted at?
2. Now that you found what your site is targeted at look to see if anyone else is ranked for the same type of website you are creating. This will be able to HELP show you if your site even has a chance to rank for the keyword.
3. Obviously examine the competition on a number type scale, analyzing pr, back links, indexed pages, domain age, onsite seo, etc..
4. Google knows what they want and how many similar types of websites the want to display for a certain keyword/phrase.
So basically we know the competition is going to be quite significant for a broad keyword like that because Google will be issuing ranking to a variety of different types of sites based off that keyword. This is explained more in detail in googles search quality raters handbook (if you had a chance to read it)
Here is another example: Buy Running Shoes
Now this keywords trigger is the "buy" statement. Google knows these people are interested in buying a pair running shoes. Pretty obvious what they type of sites they are going to be displaying for this keyword phrase. If you have a website that is based around building a running shoes website then you are going to have a tough time.
It all boils down to keyword research 101 and understand the behaviors/triggers of different keywords and phrases. Sorry for the long post, just thought I would help you nail down some solid research strategies
