An easy way is to read history, and see what things were like. It's amazing how many things that seem common sense and accepted now are from the enlightenment.
* Democracy. That one's obvious. Universal adult sufferage regardless of sex, race, creed, property ownership. We all know about "women getting the vote", but men without property used to not have the vote, catholics/prodestants/muslims/jews (delete as appropriate) used to not have the vote. Race based voting restrictions are similarly common. Some countries allow restricting voting based on criminal record (USA) other's done (most of europe), some countries prevent current criminals being elected (UK did this after some IRA terrorists were getting elected).
* Inherent rights. Who gives you your human rights? The Crown/State? So can they take them away? Does everyone have rights? Or just people/men of the right colour/creed/aristocracy? Does everyone have the same rights? No. We view that everyone has rights all the time that cannot be taken away.
* Rule of law. You/anyone should be able to know what the law is. The crown/state cannot just make up a vague law that only they can interpret. Laws cannot apply retroactively. The law should apply to everyone. It should be wrong if a certain law doesn't apply to the local lord, but it does apply to you.
* Fair trials. It's wrong that the crown/state alone gets to decide guilt/innocence, there should be an independent trial. You are allowed to argue your case. You are allowed appeal. The jury cannot be punished for how they decide your trial. You should be presumed innocent. You cannot be locked up unless you have been tried.
* Constitutionalism. There should be a document that overrides the crown/state and defined how the state works. It should list what powers the state/crown has. The King/state is not allowed to just do whatever it feels like. (Fun fact: Nazi Germany, the USSR and the USA have/had constitutions. The UK doesn't really. :P )
* Democracy. That one's obvious. Universal adult sufferage regardless of sex, race, creed, property ownership. We all know about "women getting the vote", but men without property used to not have the vote, catholics/prodestants/muslims/jews (delete as appropriate) used to not have the vote. Race based voting restrictions are similarly common. Some countries allow restricting voting based on criminal record (USA) other's done (most of europe), some countries prevent current criminals being elected (UK did this after some IRA terrorists were getting elected).
* Inherent rights. Who gives you your human rights? The Crown/State? So can they take them away? Does everyone have rights? Or just people/men of the right colour/creed/aristocracy? Does everyone have the same rights? No. We view that everyone has rights all the time that cannot be taken away.
* Rule of law. You/anyone should be able to know what the law is. The crown/state cannot just make up a vague law that only they can interpret. Laws cannot apply retroactively. The law should apply to everyone. It should be wrong if a certain law doesn't apply to the local lord, but it does apply to you.
* Fair trials. It's wrong that the crown/state alone gets to decide guilt/innocence, there should be an independent trial. You are allowed to argue your case. You are allowed appeal. The jury cannot be punished for how they decide your trial. You should be presumed innocent. You cannot be locked up unless you have been tried.
* Constitutionalism. There should be a document that overrides the crown/state and defined how the state works. It should list what powers the state/crown has. The King/state is not allowed to just do whatever it feels like. (Fun fact: Nazi Germany, the USSR and the USA have/had constitutions. The UK doesn't really. :P )