I i were to standardize morality, i would put Free Will at the center.

WE ALL have free will, therefore we are all on a common ground.
How do i know if what i am doing is right or wrong?

I DONT! NO ONE does. "Right" and "wrong" in the world of morality, are nothing more than opinions.
Right and wrong are largely nothing more than opinions, however in a few physical circumstances, there can be a right way to do something and a wrong way, but this is in no way a matter of morality and a completely seperate topic.

Free will should be the center of morality because we all possess it.
If we are respecting the free will of others, we are morally right.
if we disregard other people's wills to act, to feel, to think, then we are morally wrong.

Weather any of this is true or not is impossible to discern, for morality and right and wrong are all arbitrarily man made concepts.
Man made concepts are usually arbitrary. and the more arbitrary, the fewer absolutes.