Go to any bar/pub that has a dart board, you do not need to do this with a friend. If you don't know where to go to play darts, you can call up a friend and ask to play some darts. After you pick them up, the location will be on your radar. Once at the pub, walk up to the board and start the game with . Then, when the target is hovering over the triple 20 (inside ring, top number), press to steady your aim, throw the dart by pressing .
Then do it 2 more times in a row.
**Can be done after completing story mode**
**Note About Darts** This is for those of you who are not familiar with the rules of darts. The particular game played in the pubs is "301" which means that both players start at 301, and work their way down to 0. You need to hit 0 exactly, if you go over (under) you will bust and have to try again.
On the board you will notice 20 slices each worth a different number of points. Shoot the dart into a slice, and you will knock that amount of points off your total on your way down to zero. Along the outer rim of the board, you will notice a ring. This ring is worth double. So if you're shooting at a 20, and your dart lands in the double ring, it's worth 40. Likewise, you will notice an inner ring, which is worth triple points (and the one needed for this achievement).
Now, above and beyond simply shooting darts for this achievement, it is also required that you beat all of your friends at darts (who enjoy darts, and are needed for 100% completion). As you work your way down to zero, you need to keep in mind that your final dart that brings you exactly to zero must be shot into the doubles ring in order for you to win.
For example, if you have 13 points, shooting a 13 will bust your score (no double), as well as shooting a 14 will (going over). An example of a winning set for a 13 score would be to shoot a 3, and then a double 5 for your final dart.