The best way to do this trick is with an auto-clicker (for example, the RuneScape Auto Miner). Go to your "Equip" section and select "Train Pet", then select the pet you wish to have stats go up for. For the auto-clicker, press CTRL + A once your mouse is over the "Play Game" selection (the Frisbee-looking picture). Set your "Intervals" to "600", and make sure your event is "Left Click". Once done, press CTRL + R to start it. It will now automatically play that game with your pet for as long as desried. After awhile, you will notice the stats slowly rising by one (Wisdom, Stamina, etc.). Do it as long as desired or until you max out the pet. Without the auto-clicker, just keep pressing the Frisbee-looking picture in the "Train Pet" area.