The best way to observe a solar eclipse is:
All of these
Looking at the sun can cause permanent damage to one's eyes even on an eclipse. This is because the intensity of light coming from the sun is very high. In order to observe a solar eclipse, one should use a medium which absorbs or reflects most of the sunlight allowing just a small fraction of light to fall on our eyes. One such medium can be a glass plate blackened over a sooty flame of a candle or even a pair of tinted goggles.