Oh noes! Noses come in many different shapes and sizes so what works for one, may or may not work for another but the basic nose is fairly easy in construction. If you are looking to draw an exact replica of a nose from a reference or life, try making note of easy to identify shapes and nuances with how they connect to other pieces via angles.
Breaking down the shapes: from a cute button nose to a hooked nose that resembles the beak of a bird, the nose can be broken down to a triangular prism with spheres.
Alternative shapes: some people use cylinders and spheres. I personally use triangular prism because of the bone and cartilage structure underneath the skin. I then block the shapes to start shading.
Placement on the head: From the eyebrows to the bottom of the ear lobes.
Beneath the skin and flesh: