Usually the gender of a word in French is pretty arbitrary! And you just have to learn the gender when you learn a new word...I know that sounds scary but when you've been learning for a while, you'll find that there are some very loose rules which dictate the gender. Words ending in "-ette", "-ienne", "-elle" tend to be feminine (they are generally regarded as feminine endings..) while "-ien", "-eau" tend to be masculine.
When you're done with French, may I suggest learning German? There are three genders :)