The only numbers in play in Cricket are 15, 16, 17, 18, 19, 20 and the bull. Darts landing in other pies do not count.
In Cricket each player/team has the responsibility of scoring three marks in each of those wedges, by means of one triple, a double plus a single, or three single shots. You can not score a triple on the bull. The best you can do on the bull to complete your responsibility is one double bull and a single bull.
A perfect game of Cricket can be ended in just 8 darts, one triple in each wedge (1520) and one single and one double bull.
In real life, however the games go on much longer. This is because your opponent can affect what you do at Cricket. Strategy is most definitely a factor.
Once you have completed your responsibilities in a particular wedge, you may earn points on that wedge by putting more darts into it for score.You can keep scoring until your opponent has put his required three marks into that wedge. From that moment onward, no on can score on that wedge anymore.
To win at Cricket, you must have completed all your marking responsibilities and not be behind in score. That's three marks per wedge(including the bull) and a numerical total at least equal to your opponent's total.
The Cricket scoreboard looks much different from the simple running subtractions used in the 01 games.
The diagram at the right shows a typical game of Cricket at about the halfway point.
The player on the left, Steve, earned the right to start the game by throwing a dart closer to the bull than his opponent, Don. Steve began by aiming at the 20 wedge and hit only one 20 in his first three darts. That mark is scored with a single slash on Steve's side of the scoreboard. Don stepped up to the line and fired a single 20, a miss and then a triple 20. The circle to the right of the number on Don's side of the scoreboard represents him having closed the 20s (hitting his required three marks).He shot a fourth 20, so this is recorded as scoring 20 points, shown at the right edge of the scoreboard. On Steve's next turn, he hit two 19's and Don answered with one 19, a miss and with his third dart 
decided to try to score on the 20's since Steve had let it open. He hit a single 20 and his total score increased to 40.
Now its Steve's turn, he aims for the 18 and hits a triple 18 with his first dart. He could continue throwing 18's for score but he elects to move to the 17 wedge. He hits a triple 17 with his second dart and continues on the 17 with his third dart for score.
Next shot for Don is a triple 18. He can not score on the 18's because Steve already closed them, so he moves on to the 17 wedge hitting two singles to end his turn.
Don pauses to figure out his next move. He could advance the game by trying to close more wedges. Or he could go back to the 20's and score more. Or he could throw some to close and some to score. If he is conservative, Don will score more 20's. If he is aggressive he will try to finish the game by closing numbers. He is barely ahead of Steve just now (exactly even on marks and up by 23 points). He'll base his decision on how accurate he thinks he is versus how good he thinks Steve is.
This game could conceivably end with no more points being scored by either player.But that's very unlikely.The player who gets behind on marks usually tries to get ahead on sore, to lengthen the game and give the enemy a margin for error. Remember, the game isn't over until someone has closed all the wedges. And the winner must not be behind on score, even if he's closed his wedges.
Learning when to score and when to close is the fine art of Cricket
___Steve___________Don________
17 / 20 O 20
X 19 / 40
O 18 O
O 17 X
16
15
B
