OP By "veteran" they mean "Battlefield Veteran" and not actual military veteran. Veteran status is calculated by taking the total number of Battlefield games played and subtracting 1 (i.e. if you played Bad Company2 and Battlefield 3 your veteran status would be 2-1=1, if you have only played Battlefield 3 it is 1-1=0 or no veteran status) because you are only a Battlefield game veteran after playing more than one game - veteran status is not dependent on rank in Battlefield 3, only the number of Battlefield games that you've played in the Battlefield series.
The easiest way to automatically update your veteran status is to play the Battlefield games while logged in with your Origin account - this will automatically update your status. The veteran page here http://www.battlefieldbadcompany2.com/veteran is the next best way to update the status manually, for newer PC\Console releases it will automatically update when you hit "refresh veteran status" or play the games while logged in with your origin account. On the lower part of the page you can enter the CD keys for the older PC only games by clicking on the game's icon. You can also update the game expansions that do not contribute to your veteran status by selecting the expansion like Euro Force and then entering your Gamespy ID and password.
If you have only played BF3 you can get veteran status very cheaply by buying a used copy of Battlefield Bad Company 1 or Bad Company 2, buying BF1943 (digital only BF game for around $15 USD) which should all be very inexpensive in the used section, or you can play one of the free web based Battlefield titles such as Battlefield Heroes http://www.battlefieldheroes.com/en/ or Battlefield Play 4 Free http://battlefield.play4free.com/en/ while logged in with your Origin account. These two titles will give you veteran status as well.
