I always see this simple tables, where inclination is determined very easy - you just look if it's feminine, masculine or neuter and then look at the ending of the word.
But it just doesn't work sometimes.
"звено" - "звенья" but
"зерно" - "зёрна" and
"шило" - "шилья". Sometimes it works several ways like
"крыло" - "крылья" but
"крылА" works as well (although sounds a bit old-fashioned).
Is there some more general rule or I'll just have to memorize all this? I'm especially interested about "зерно" and "звено", they appear so similar!