In sentences with one simple verb, the direct object pronoun comes before the verb.
Yo la veo.
I see her.
Carmen no lo lee.
Carmen doesn't read it.
Manuel la tiene.
Manuel has it.
María no los tiene.
Maria doesn't have them.
Mi hermano las compra.
My brother buys them.
Infinitives and Present Participles
In the case of infinitives and present participles, you either can attach the direct object pronoun to the end of the verb or put it before the first verb.
Voy a hacerla.
I am going to do it.
La voy a hacer.
I am going to do it.
Estoy limpiándola.
I am cleaning it.
La estoy limpiando.
I am cleaning it.
Note the accent on limpiándola. This is used to preserve the stress on the correct syllable.
Affirmative and Negative Commands
Direct object pronouns are always attached to the end of affirmative commands.
Direct object pronouns always go between the negative wor(no, nunca, etc.) and the verb in negative commands.
Léalo.
Read it.
No lo leas.
Don't read it.
Sácala.
Take it out.
Nunca la saques.
Never take it out.