Explanation: "Always" = SIEMPRE. It naturally goes at the start or before the verb phrase: Siempre me levanto temprano.
Explanation: "Sometimes" = A VECES. Like most frequency adverbs, it can start the sentence: A veces como pescado.
Explanation: When nunca follows the verb, "no" must come before the verb — the double negative is required in Spanish: No como carne nunca. (Nunca como carne is also correct.)
Explanation: "Every day" = TODOS los días (masculine plural agreeing with días).
Explanation: "Los + day" means every week on that day, with no preposition: Los lunes tengo clase. "En los lunes" is an anglicism.
Explanation: "Times" in frequency expressions = VECES: dos veces a la semana (twice a week), una vez (once — singular).
Explanation: "Hardly ever" = CASI NUNCA (literally "almost never"). Casi siempre = almost always; a menudo = often.
Explanation: Unlike siempre/nunca, MUCHO goes AFTER the verb: Viajo mucho.