Say "¿Habla inglés?" to ask someone if they speak English. This is a useful phrase to have when one encounters communication difficulties in a Spanish speaking country.
Ask, "¿Hay alguien aquí que habla inglés?" when you want to know if there is someone here who can speak English.
Learn to say, "¿Entendiste eso?" to say, "Did you understand that?" To answer this question you could respond in two ways: "Sí, entendí eso" (Yes, I understood that) and "No, no entendí eso" (No, I did not understand that).
Command that someone speak more slowly by using the phrase, "¿Podría usted hablar más despacio, por favor?" Spanish speakers tend to speak very fast, so this phrase will come in handy in several situations.
Request that someone repeat a phrase by saying, "Repite, por favor." You can ask someone to write something down by saying, "¿Podría escribir eso para mi?"