How do I know if I broke a toe?

Pain. Usually a broken toe will swell, bruise, painful to touch, can't move it without pain, and maybe appear misaligned. The only way to be sure about a fracture is to get an x-ray.
X-ray. Xrays are simple and are a first line tool in determining the presence of a fracture.
X ray. If it is misaligned, it is probably broken or dislocated. If it is in good alignment, but is painful when you squeeze the toe from side to side, it is possible that it is broken. Have it evaluated. Dr l.