Nature of science
Understanding how science works allows one to easily distinguish science from non-science. Thus, to understand biological evolution, or any other science, it is essential to begin with the nature of science.
What is science?
Science is a particular way of understanding the natural world. It extends the intrinsic curiosity with which we are born. It allows us to connect the past with the present, as with the redwoods depicted here.
Science is based on the premise that our senses, and extensions of those senses through the use of instruments, can give us accurate information about the Universe. Science follows very specific "rules" and its results are always subject to testing and, if necessary, revision. Even with such constraints science does not exclude, and often benefits from, creativity and imagination (with a good bit of logic thrown in).