a Good boy holds the tournament on its computer. call him the 'organizer'
he defines the rules of the tournament (realistic or not, stock or DSL, weight, etc).
each competitor send its bots.
the organizer makes AI to the received bot so they can fight without a human driving them (much as those you meet when you play events on RA2).
the organizer publishes the result.
Most famous tournament is Bbean :
http://beetlebros.gametechmods.com/bbeans/hof.htmbut some other tournaments keep growing (Clash Cube, RAW, etc). see on this forum, there is the list of current tournament, those who will come soon.
ACAMS also holds other kind of contest : show contest with BOTM (bot of the month).