How do you tell what words are masculine or femimine?

Question

I have an assignment due in a couple of days but I don't know which is what

Answer 1

You can't. Period. If you don't know the word at all, depending on the ending you have different probabilities. Words ending in -o are 99% masculine, as there are only a tiny handful of words that are not. A notable exception is "mano", which is feminine. Words ending in -or are also masculine except for four of them. Words ending in -a are not that reliable, as there are quite a few masculine ones with this ending, and quite a lot that can take either gender. Practically all words ending in -ión are feminine. There are many other thumb rules, but inevitably, there are words that simply have to be memorized.

Answer 2

Try looking here: http://www.spanishdict.com/answers/100009/nouns-gender