It's always best to learn them together with the noun. There are some rules, but there are a lot of exceptions. To make it easier: nouns that end with -keit,-heit,-ung,-tät,-schaft,-ik,-in,-e (but der Löwe, der Pate etc) are usually feminine nouns with -ismus,-er are masculine (der Leiter: leader; die Leiter: ladder!) nouns that end with -chen,-lein and that start with Ge- But don't rely on these rules to much, the exception proves the rule :-)

Here are some tricks regarding this problem: http://www.italki.com/notebook/entry/13850.htm http://www.italki.com/notebook/entry/13851.htm http://www.italki.com/notebook/entry/13852.htm