Check for the correct usage of expressions, as this easily reveals a writer's familiarity with the language. An expression is a group of words that communicates a particular meaning beyond the literal. Because of the non-literal nature of expressions, they cannot be translated directly from one language to the next. For example, if you want to write "you're welcome" in Spanish, you might directly translate that to "Ud. es agradable." Unfortunately, this would not really make any sense. The correct expression would be "de nada," which roughly translates to "it was nothing" in English.
Look for the correct usage of accents throughout the paper. For example, common words like "tú" and "él" have accents that are commonly forgotten. Additionally, the accent in a word may shift or disappear when it it changed from its singular to plural form or vice versa. An example is the word song, "canción," which has an accent in its singular form but loses it in its plural form "canciones."
Analyze the paper for its use of proper subject-verb agreement. If the paper is trying to say "he walks" (in the present tense), make sure that he writes "él camina" and not some other present tense form of the verb (such as "caminas" or "camino"). A more advanced way to determine writing level beyond subject-verb agreement is determining whether the proper tense of a verb is being used. If the writer meant "he walked" (at one specific point in the past), it should be written "él caminó." If he meant "he walked" (at various points in the past), it should be written "él caminaba."
Check for the proper placement of an adjective in relation to its corresponding noun, and look for the correct agreement between a noun's number and gender and that corresponding adjective. In Spanish, the adjective comes after the noun, so lower-level Spanish writers may accidentally put the adjective first ("gato bonito" or "cat pretty" is correct). For a more advanced criteria, check for number and gender agreement. For example, "las canciones largas" equates "the long songs" in English. Because "canciones" is feminine and plural, its corresponding adjective must end in "as."