Sharpen Performance Tip
Sharpening a performance tip makes the Beyblade spin in place more. Rather than loop around the arena, the Beyblade stays put on its sharp spindle, making it a more defensive Beyblade. If you have a lathe, you can attach the performance tip to the lathe and sand the bottom with a rough grit, like 60, and then polish it to a smooth sheen with 1,000 grit. If you don't have a lathe, try attaching the performance tip to a power drill and sanding the bottom in the same way.
Flatten Performance Tip
Flattening a performance tip makes the Beyblade more aggressive because there is more surface area upon which the Beyblade spins. The Beyblade loops in big arcs around the arena, crashing into other Beyblades and, hopefully, knocking them off balance or out of the track. Flatten a performance tip by taping rough sandpaper onto the surface of the track and launching the Beyblade onto it. The Beyblade's own momentum will sand the bottom. Replace the rough grit with a softer one to then polish the bottom of the performance tip.
Considerations
If a Beyblade's performance tip is not well-balanced, it can lean to one side or the other. You can use this a strategy if you always want your Beyblade spinning off to one side or the other of the track, but in most cases the imbalance causes the Beyblade to oscillate, which means it loses energy faster. In Beyblade parlance, it then has a low stamina. If you can't evenly sharpen or flatten your Beyblade's performance tip, don't do so.
Special Cases
Some Beyblade's have performance tips with multiple parts. You can adjust these parts to improve the Beyblade's performance. For example, Storm Pegasus has a two-part performance tip: the housing and a red rod through it upon which the Beyblade actually spins. Push the rod out of the housing with your fingers. Insert an eraser or other kind of button into the spin track that holds the performance tip. Place the performance tip assembly back on the spin track and force the rod through the tip. Now the rod sticks out more, making it the entire Beyblade taller and more aggressive.