1. Using a written accent mark. An accent mark (´) is placed over a vowel to indicate that the vowel is stressed. For example, the word "árbol" (tree) is pronounced with the stress on the first vowel, so it is written with an accent mark: "árbol".
2. Using a phonetic change. In some cases, the stress of a word can be indicated by a phonetic change in the vowel. For example, the word "casa" (house) is pronounced with the stress on the first vowel, but the stress is not indicated with an accent mark. Instead, the vowel "a" changes to a different sound: "casa".
There are some general rules for where the accent mark is placed in Spanish words:
* Words that end in a vowel, "n", or "s" are stressed on the next-to-last syllable. For example, the word "mesa" (table) is stressed on the first vowel, so it is written with an accent mark: "mésa".
* Words that end in a consonant other than "n" or "s" are stressed on the last syllable. For example, the word "pared" (wall) is stressed on the last syllable, so it is written without an accent mark: "pared".
* There are some exceptions to these rules, but these are the general guidelines for where the accent mark is placed in Spanish words.