The rule for the accents is very easy, the problem you might have is when words have a diacritic accent. Just forget about the accent. An easy advice I'd tell you is this: don't try to learn it as "The word with, and without accent", just try to see it as two different words, like Como = like, Cómo = how, si = if, sí = yes, di = gave, dí = say" etc.

The rule is: a word that ends with "a", "e", "i", "o", "u" (vowel), or "s" or "n" is accented on the before the last syllable like GAto, CAsa, muCHAcho, REglas... (By accent I mean when you speak, not written) a word that ends with a consonant (except "s" and "n") is accented on the last syllable like veLOZ, deCIR... When a word doesn't respect this rule, there is a written accent. Tomás, lápiz, ejército, teléfono... So it means that you need to know how to pronounce the word but practicing you will realize it soon. Did I help you?