A pool cue is a player's most vital piece of equipment and the cue tip is equally important. The cue tip must be shaped to give the shooter the best play out of his shot and, generally, the tip is shaped to suit the style of shooting performed by the player. Numerous tools are available to shape or sand down a cue tip, most of which are shaped to the radius of a 2p piece. The radius and edge of the tip is completely down to the shooter's discretion, while the shaping process must be done with extreme care to not remove too much material, or scuff the ferrule -- the white plastic end piece. Shaping tools or sandpaper files are best for cue tip shaping.
Determine what kind of shooting you need to perform. If you tend to put a lot of spin on the ball, then you'll want a tip that has smooth, rounded sides, and this will require more sanding. If you're more of a straight shooter, then a less rounded tip with hard edges is the ideal shape.
Place a pool shaper on to the tip. A Williard shaper or Cue-cube are the most popular shaping tools and work great for most shaping. Use extremely light pressure, and twist the shaper about a 6.5 mm (1/4 inch) turn at a time, then inspect the tip. You'll notice that the edge will be slightly rough, and some material will have been stripped off. Continue this process, a turn at a time to round the tip edge until its rounded to your specifications.
Use a fine 500-grit sandpaper file to smooth out the tip where you used the shaper. Hold the file at a 60-degree angle over the tip and smooth out the edge, 6.5 mm (1/4 inch) at a time.
Hold the sandpaper file flat on to the tip end and rub back and forth until the tip is smooth. If you need to round off the edges, slide the file down over the tip edge. Ensure that no nicks or scuffs are visible on the cue tip. When you're finished, you'll have a completely smooth cue tip.