Hey, this is for all of you who come on and want to learn to box and get some fights, but don't know how. Each of us with some experience will post how to go about doing it in our respective countries. I'll start with the US
Competing in USA Boxing:
To do this you'll need to find the registration chair for your LBC. USA Boxing is composed of LBCs (Local Boxing Committee) and is responsible for the registration of all people in their jurisdiction. For example, if you live in Washington DC, you would register in the Potomac Valley Association LBC (and as an aside, you would need to go to Sugar Ray Leonard's gym to do this). This is a full list of the LBCs in USA Boxing: http://boxing.usoc.org/content/index/43
To register you'll need 2 passport photos and a copy of your birth certificate, and if under 18, you need a parent signature. It costs 40 dollars a year and you're registered for the whole year that way. You'll be given a USA Boxing passbook which will over time reflect the record of the fights you've had. From there, you just need to get in a gym and get to work (typically, you would get your passbook after being in the gym a while, though). Also, as a note, you don't need to be with a gym to get registered. When the registration chair asks what club you're with, just say you're unattached.
Also, an extra note: the Golden Gloves is NOT a seperate sanctioning body. It is a franchise that is a member group of USA Boxing, along with the National PAL. Golden Gloves is a major ranking tournament that, like the USAs, begins at the LBC level, progresses to the regional (or in the case of Golden Gloves, franchise) level; and if you win that are on to the National Championships.