It's more like a dictionary lookup[0] than some general pattern. Also there are many regional variations. So if you have come across a particular lastname before you happen to know they are brahmin.

[0] - https://www.momjunction.com/articles/brahmin-caste-surnames-...

It depends on area/region/language/place, so it's probably too way too many to list.

You can look at common conventions here: https://en.wikipedia.org/wiki/Indian_name