|Recognizing the PBA:
Intel PBAs are always six digits, followed by a dash, followed by three digits (i.e.: "123456-789"), and, in most cases, the letters "PBA" are right in front of the number.
Finding the PBA:
To find the PBA, the most likely place is near one of the board edges. The PBA can usually be found on a small, white sticker, or sometimes on a small, yellow sticker. If not near the edge, try looking at the middle of the board. In some cases, the PBA is put on the bottom of the board.
Other useful numbers:
Other numbers that you may find in your quest that can also be helpful are the PB number and/or the AA number. The PB number is almost always found on the bottom of the board and is etched in the copper. The AA number, which is only found on some boards, is usually on the top, in the same areas as you would normally find the PBA.