How does one implement their duties according to the Bhagavad Gita?

I'm a bit confused with how one figures out whether one is a brahman, a ksatriya, a vaisya or a sudra in this day and age. Could someone please explain this?

There're various ways one can

There're various ways one can ascertain one's varna, e.g.:
http://veda.harekrsna.cz/encyclopedia/varnasrama.htm#6

Hari Hari
ys Jan