In darts, you have to go down from 301 points to the 0 by hitting in the particular places on the board. Big fields (white and black) are worth the number written on them. Small fields (red and green) making two circles are doubled on the outer circle and tripled in the internal one. Hitting the middle of board gives 25 or 50 points, if you get in the very middle (bullseye). Remember, that to finish the game you have to hit the multiplied value from circles or from the middle of board. In other words, if you need 6, hitting 6 won't end the game. You have to hit a triple two (inner ring) or double three (outer ring) to finish. If you hit the six only or anything more, you won't end the game and you bust your turn.
You throw the dart with A/X. You aim with the left analog. You can also hold RB/R1 to speed up throws. Sight will tremble a bit to make your task more difficult and you can stabilize it for while by pressing RT/R2. When you begin the game, try to always aim at the triple twenty. When you do it three times in a row, you get down about 180 points and then you can win in the second turn when you just need to get rid of 121 points. You can hit then, for example, triple twenty (71), triple seven (40) and double twenty (0).