The subjunctive is used with verbs of influence, such as those shown below:

querer - to want
preferir - to prefer
desear - to desire
insistir en - to insist
mandar - to command
prohibir - to prohibit
requerir - to require
exigir - to demand, require
recomendar - to recommend
pedir - to request/ask for
alentar - to encourage
decir - to tell, say (when not used as a verb of reporting)

Put the verbs above into the formula below to express influence over actions that the subject would or would not like somebody else to do, but cannot directly control.

Subject 1 + verb of influence (indicative)
+ que + Subject 2 + action to be done (subjunctive)

El profesor quiere que tú hagas la tarea.
The teacher wants you to do the homework.

Yo quiero que Juan me ayude a limpiar la casa.
I want John to help me clean the house.

Tu madre desea que hables con ella.
Your mother wishes (wants) you to talk to her.

Ella prefiere que vayamos en tren.
She prefers that we go by train.

Exigen que pagues más.
They demand you to pay more.

Yo pido que vengas.
I ask you to come.

Luis desea que Paco vaya al río con nosotros.
Luis wishes that Paco comes to the river with us.

¿Insistes en que lo hagamos?
Do you insist that we do it? (Or: Do you insist on our doing it?)

Recomiendo que salgas.
I recommend that you leave.

¿Manda él que yo lo escriba?
Is he ordering me to write it?

Piden que cenemos allí.
They're asking us to dine there.

No permitimos que lo compres.
We don't permit you to buy it.

Note: The presence of one or more verbs of influence is not sufficient to require the use of the subjunctive. There must be two subjects and one subject must attempt to influence the other.

Yo quiero venir mañana. (indicative)
I want to come tomorrow.

Yo quiero que Uds. vengan mañana. (subjunctive)
I want you all to come tomorrow.