WHAT A YEC IS:
A young-earth creationist is someone who takes the accounts of the Bible, specifically Genesis 1-11, as actual historical fact as written. This view contends that God did create the world in six literal 24-hour days approximately 6000 years ago. YECs reject unobserved sciences such as macroevolution (animals changing into other “kinds”) but accept observed sciences such as microevolution (natural selection & variation with created kinds). The view also contends that the earth was decimated in a catastrophic worldwide flood that is to thank for most of the geologic strata and fossil record. Most YECs agree that dinosaurs were created on day six of creation, lived alongside man, were most likely on the Ark, and died out sometime afterwards. YECs point to unverified assumptions in unobserved sciences such as dating methods as to where they have gone wrong. The whole viewpoint boils down to this: creationists and evolutionists have the same evidence, different conclusions, based on different starting points.
WHAT A YEC IS NOT:
A young-earth creationist does not ignore evidence; they just have a different conclusion about the evidence based on a different set of starting assumptions. Most YECs have a thorough understanding of evolution. It is hard to speak out against it without understanding what it is. They do not need to “take a class in biology” as often suggested. YECs do not promote a deceptive God theory. Many evolutionists contend that God must be deceptive is he planted so much wrong evidence to deceive us. The YEC response is that it is not deception; it is incorrect human interpretations of evidence stemming from ignorance of Biblical revelation. Ignorance, not deception.
My main argument for old-earth creationists would be to examine if that position is compatible with the concepts of no death before sin (Romans 5:12), God’s own declaration in Exodus 20:11 that he created in six days, and the reason needed for a savior if death/suffering has always been a part of creation (as the secular interpretation of the fossil record suggests).
My main argument for evolutionists is that macroevolution is unobserved, and unrepeatable and therefore not strictly science in the same way that gravity is. Therefore large scale evolution requires a faith element to believe it. The starting assumptions for evolution can never be verified (in the same way that the YEC assumptions cannot as well). Both are logical deductions IF their starting conditions are true.