genitive plural

is there a way to know for sure what the genitive plural of a noun is?

i know that ov, ev only applies to masculines and neutrals but i'm totally lost when it comes to using ey or nothing.

Sure: ей for nouns ending in a soft sign, take off -a or -о for feminines and neuters.

Oh, and don't forget nouns ending in ие and ия ........replace the я or е with й

And remember that when you take away those a's and o's and your word ends on two consonants - you are in deeeeeep trouble. Because you have to put in letters between those to consonants usually e or o. Have fun!

Studying Russian is fun, is it not?