There are a number of different configurations of the classic 'two turntables and a mixer' set up in use by various DJs, based upon preference of the DJ. See the varying configurations below, along with their pros/cons.
The 'normal' style is so called because it is how Technics branded the SL-1200 for DJ use; either side of the mixer.
The L style was made famous by some members of the X-Men and its main benefit is the placement of the start/stop buttons close to the mixer.
The Philly style was invented by some Philadelphian DJs, and it is useful because a large amount of the record area is directly in reach and the tone arms are tucked away and therefore unlikely to be knocked. Some turntables are manufactured with dual start/stop buttons and other controls, in order for them to reachable in Philly style.
One scratch handEdit
The one scratch hand style is useful for DJs who are only comfortable with record control on one hand, or need to do this for some specific trick.
The odd styleEdit
The odd style is useful with turntables that do not prevent the tone arms being turned away from their main area, and thus can place the two tone arms on the one record. This technique was pioneered by DJ Woody, using Vestax turntables.
This is obviously not correct. There is no way that either tonearm can reach in this configuration. Physics.
An example of odd style can be seen []