What is a "Mainstream" applicant?
Most schools don't attempt to define a "mainstream" applicant, one for whom no special consideration will be given. Instead, they define their special consideration categories. Everyone else is "mainstream" by default. While this approach makes sense to the law school, the applicant may find it helpful to have a starting point.
The socioeconomic profile of the typical law school applicant looks like this. He or she has at least one parent who is a college graduate, and who works at a white collar or professional job. The applicant usually did not need to work during high school or college, except for pocket money. Her or his household chores were limited to the kind of jobs typically associated with students: doing dishes or yard work, baby-sitting, helping with dinner. The typical law school applicant did not have to work full-time during school, take care of an ill or disabled parent, or bear primary responsibility for younger children while all available adults worked.
How does being "mainstream" affect me?
To the extent that you meet this profile, you are a "mainstream" applicant. When the law schools are choosing people to be on their team, they will see nothing interesting about you, and you will be accepted at those schools where your GPA and LSAT themselves are interesting (i.e., at or above median). You can increase your diversity value (and thus lower the numbers you need to get in by a few index points) in two ways:
What will set me apart?
I don't know. The things I'm talking about are "entirely personal," and I don't know you. In my admissions service, I work very hard with mainstream clients to find their diversity. Some examples I have found quite interesting (and effective) are:
Each of these things added a dimension to the applicant that socioeconomic and demographic factors could not show.
Where do I show these things?
These examples are the kind of things admissions officers mean when they say that a personal statement should show "what makes you unique," or "some personal insight." The personal statement is the best place to show this diversity to the admissions committee. Such diversity can be worth 2 to 4 index points in the admissions process.