I check the most recent. I'll also look at any recent very high or low score reviews. I don't put much weight on extreme reviews -- but want to see what may have triggered them. It's usually just a matter of taste, which I discount. Basically if I am already interested, if she doesn't have a terrible average, I'll book.

more accurate the averages are.  I will usually scan the scores first for the last year and see if the more recent ones are trending up or down.  Then I will look for reviewers I know are legit and read their reviews.  If she doesn't have any reviews from guys I know, then I will pick six from the last 3-6 months, and read the highest, the lowest, and four in the middle.  I'll make my decision from that.  

I will look at the latest reviews. Look at one or 2 of the oldest reviews. Look for reviews that are 6s and read those.  

Generally, if I am looking for a new provider to see, its because I am traveling to a new city for vacation. I will just look at the top 100 until I find someone in my budget who will see my demographic whose services I like and I find attractive.

The most recent reviews can give a better idea of the service being offered currently.  When reviews are in the higher amount and go back a few to quite a few years, service can change. I've noticed with a few of the providers I was looking at and their reviews went from pretty open and wild to a lot tamer! The skill level was better or perfected, but some things were off the table! DFK, GFE and no routine were gone and replaced with a set, straight forward session. A good session, just not open or following the mongers lead!  
    If it was someone I really want to see I would read all their reviews. I like to go with the lower scores first to see either where the monger went wrong or the provider didn't honor her menu. Or, she didn't like something about him and how I can make it work for me! I might look into the reviewers other reviews to see how he rates or interacts with other providers.
      I might even search the boards for info on the provider and PM a reviewer with a direct question.
      I've done pretty good with my way of researching a provider I'm interested in, but I can always improve on the process and learn new tricks!  
    I was thinking about starting a thread that asked if any mongers read the reviews of providers after they've seen them! And, why or why not!

I look at her profile and make sure we are on the same page about what we like to do.

I look at her average scores and look for a trend in review scores over time. I read a representative recent review (preferably by someone I am familiar with) and maybe an outlier.  

I make no effort to read a bunch of reviews on a provider, and don't really care how many she has.

and also check out the review history of those reviewers to see if they are easy or hard graders.

 
I also scan the earlier reviews to see if there are any by members whom I am familiar with.

 
For the investment of time, effort, and money, I think it is worthwhile to do as much research as I can; plus I rather enjoy the process.