The first thing that pops into my head
is that anyone who can always fill the basic needs of life (a pair of shoes, food, a tank of gas and a dependable car), without planning ahead is middle class.
Of course there are many ways to define class that involve more than money but they do not immediately pop into my mind.
I have found that people with more education tend to be in a different class, not neccessarily better but definitely different.
And, then there are those who glitter when they walk.