Changing the pH level?

I need help and dont understand how to change the pH level from say 9 to 10, or 9 to 8! please help!Changing the pH level?
If you want to make the soil (I'm assuming you want to change the pH of soil?) more acidic, you would add things that are lower on the pH scale:

*Lemons

*Vinegar

*Lime

Basic:

*Aluminum Sulfate

*Sulfur (However this takes longer)Changing the pH level?
pH is the negative decade logarithm of the concentration of H+ ions. so you have to change this concentration in order to change pH. this can be done by adding an acid (pH goes down) or a base (pH goes up). or you could stabilize the pH at a certain level with a buffer.