Making straight cuts in ceramic tile is usually just a matter of scoring and snapping it on a tile cutter, but curves, angles and other custom cuts require a rod saw. This is a hand-held tool that looks like a small hacksaw, with a thin, rough carbide rod as a blade, which can saw around almost any contour. The trick with a rod saw is to make sure the blade cuts into the glazed surface only during the forward strokes, to prevent chipping.
Mark the shape that you want on the face of your tile, using your wax pencil. Mark it clearly and firmly so it doesn't wipe off as you're working with the tile.
Set the tile in a mounted vice with padded clamps. Make sure the main part of the drawn design is standing up out of the clamps, vertically.
Hold the blade of your rod saw against the edge of the tile, at a point where the line meets the edge. Push the saw forward, tilting the blade slightly down toward the direction of the face, so it's going through the glazed surface of the tile before it goes through the body of the tile.
Draw the blade back toward yourself, straightening out the saw as you do, so the blade isn't cutting through the face of the tile as it comes back toward you, but only through the body.
Repeat the process, tilting the blade down toward the surface as you push it forward, and straightening it out as you pull it back. Follow the contours of the wax lines as you continue to cut through the whole face of the tile, readjusting the position of the clamps as necessary.
If you're planning on cutting patterns into more than just a few tiles, a hand-held rod saw will be slow going. There are motorised versions of a rod saw that you can rent from your home improvement store. They are set up like band saws, so instead of sawing at the tile, you feed the tile through the saw, turning it as needed to follow the drawn shape.
Always wear eye protection when cutting tiles.