The easiest way to make a sentence negative in Spanish is to put no in front of the verb. For example:
When answering a question, no is often repeated for emphasis, eg No, no tengo hermanos (No, I don't have any brothers or sisters).
No must go after the subject and before the verb, eg Mi hermano no es alto (My brother is not tall), Los jóvenes no estan contentos (The young people are not happy).
Never separate direct or indirect object pronouns from the verb. Simply place the negative word in front of the pronoun, eg no lo conozco (I don't know him), no lo he visto (I haven't seen it).
Some other useful phrases with no are: