Masculin:
1) Words ending in -age, -eau, -ou, -illion, -er,-isme,-ment,-oir are masculine.
2) Les jours (days), les saisons(seasons), les lettres de l'alphabet (letters of the alphabet when spelt out), les nombres (numbers when pronounced) are masculine.
However, there are some exceptions: la page (the page) , la cage (the cage), la mer (the sea) are feminine though they have endings of -age, -er, etc.
Feminine:
Words ending in -e,-oi,-sion,-tion,-té,-gion, -aison,-ance,-anse,-ence,-ense are all feminine.
Branches of learning, religions festivals are feminine. La litterature, la philosophie, la chimie, etc.
Here again we have exceptions: le roi (the king), le silence, en été.
Au revoir!