Hello!
1. Voy a trabajar en tren. Me gusta ver todo el paisaje. Por eso, quiero un asiento de ventanilla.
Why? In this statement, this person wants to see the entire landscape, so therefore, he wants a window seat.
2. ¿Quieres llamar a Jorge ahora? -Si me voy a llamar dos minutos.
Why? Irse is reflexive in this case, and "voy" has the subject I, so therefore, "me" is appropriate for this because of the reflexive rules.
3. Señora, ¿le traigo más café? -Gracias, señor, tráigarme más café por favor.
Why? Le traigo is reflexive, so therefore, the word missing has to also be reflexive. "Tráigarme" means to "bring me more", and the woman wants more coffee.
4. Voy a ir a Costa Rica y nunca voy a volver. Voy a comprar un boleto de ida y vuelta.
Why? "Boleto" means ticket, and "boleto de ida y vuelta" translates to "round-trip ticket".
5. Les doy muchos regalos de Navidad a mis amigos.
Why? "Les" is used in this phrase because you are giving it to your friends.
6. Cuando viajamos a otro país, hay que pasar por la aduana.
Why? Normally, if you travel to another country, you would have to go through customs in order to legally enter the country. "La aduana" means "customs".
7. ¿Conoce usted dónde está él Parque Colón?
Why? Conocer and saber means to know, but it has different meanings. Saber means to know factual information, or how to do something. Conocer means to be familiar with something (abstract information), like a city, park, person, etc.
8. Quiero hacer un viaje a Chile.
Why? Hacer is best used in this sentence because they want to "take a trip", which translates to "hacer un viaje".