The more you win, the more skill points you earn. For each level player gets 1 skill point up to level 30. After level 30 skill points are not given.
You can customize those skill points to Speed, Strength, or Smartness parameters. To spend a skill point go to your profile (profile tab is in the upper right corner of the page) and apply it to any stat you want. You can also skill up your parameters with the shoes and gloves from the Proshop. Certain shoes or gloves can add +2/+3 to your Speed or Strength.
Strength
Increasing your Strength will allow you to throw heavier balls. With Strength 10 you can use a Power 10 rated balls. A higher Strength will open up more options in the Proshop as well. Maximum Strength is 16. You can get 10 Strength points by leveling up and 6 extra points from shoes and gloves.
Speed
Speed 1 allows the ball to go a maximum of 13 mph, while Speed 10 will see the ball reach a maximum speed of 21.3 mph. The faster you throw the ball, the more pins you can knock over. Maximum Speed is 16.
Smartness
Smartness increases all chips and coins earned or bought by 2% at the very beginning and by 20% when skilled up to 10 rating. The same way Smartness affects experience. Maximum Smartness is 10.