Your dog can only learn a certain amount of tricks a day, while the same goes for competitions. To get additional chances at tricks and competitions, change the system date to to the previous day and set the time to 23:59. Exit the menu and turn off the DS. Immediately turn it back on and load the game. You will see the previous day and time shown. After one minute it will be an entire new day, allowing more tricks to be taught and competitions to be won. This can earn you more money if you win the competition. When you want to follow the normal order of things, just set the date and time back to the correct values.