You have to be careful because there are countable and uncountable noun so that you can't put s even they are plural. Foe example: "information", it's absolutally plural and uncountable noun so you can't make it as "informations", then "children", it's plural form of "child" so that you can't write it "childrens".

It's worth trying your best with the irregular plurals, so hopefully the lists offered by other members will help. There are two basic reasons that a noun may have an irregular plural: 1) The noun follows old Anglo-Germanic rules. There exceptions are common daily things (especially to a working farmer): men, mice, geese, fish, sheep, lice, oxen, brethren... 2) The noun is a borrowed word, and also borrows the plural form from the other language. "Cacti" and "fungi" come to mind. Trying to make an English plural by adding "s" may sound awkward. And then there are the uncountable nouns...

English is full of irregular words so generally add -s to make the singular plural and you just have to learn the irregular nouns. (sorry but that may be as good as it gets )

Have a look at 'Plural Noun Forms' at http://grammar.ccc.commnet.edu/grammar/plurals.htm