As mentioned here, it’s usually not difficult to determine whether a word is masculine, feminine, or neuter in Russian. It only becomes tricky when a word ends with a soft sign, the мягкий знак or ь, and there are many such words. A useful tip: they are never neuter. As for the rest — masculine or feminine — these rules will guide you.

Every noun in Russian is masculine, feminine, or neuter. You always need to know which category it falls into, and usually, that’s not difficult. Words ending in a consonant are masculine, words ending in а or я are feminine, and words ending in о or е are neuter.