Reason, Impetu or cause:

• Lo hizo por bueno
  • He did it for [the common] good.
• Esto es por ti
  • This is because of/due to you [your fault].
• Fui por agua
  • I went for [my motivating factor] water

including Instigating person agent or person

• Lo hizo por ti.
  • He did it because of you/of what you did (you made him do it.
• Fue construído por Mauricio Izquierdo
  • It was built by Mauricio Izquierdo.

End Goal (Purpose):

• Estudia para ser médico.
  • He's studying to be (in order to be) a doctor.
• Voy para aprender más
  • I'm going in order to learn more.
• Fui para llenar el tanque.
  • I went to (in order to) put gas in the car

to indicate direction or path of movement:

• Voy por Toledo
  • I going through or in the direction of Toledo
• Voy por el norte.
  • I'm heading north

Physical Destination [You can often sustitute "hacia" for para]:

• Voy para Toledo
  • I'm going to Toledo.

to indicate a Duration or Passage of time:

• Será por agosto.
  • It will be in August, during August
• María cantó por dos horas
  • María sang for two hours

Time Limit or Destination:

• Voy para agosto
  • I'm going by August) (deadline)
• El informe es para las cinco de la tarde.
  • The report is for (due by) 5pm.

substitution/exchange

• Pago $25.00 por la novela
  • I pay $25.00 for the novel.
• Doy el libro por el otro
  • I give this book for the other [book].
• Trabajo por ella.
  • I'm working for her today (in her place.)

Recipient

• Este regalo es para ti.
  • This gift is for you.
• Trabajo para ella.
  • I work for her (she is my employer)