1. Wrong: we wanted to visit phoenix, arizona, but my family thought it would be too hot.
Better: We wanted to visit Phoenix, Arizona, but my family thought it would be too hot.
Explanation: The first letter in the sentence and the proper noun/name of a city need to be capitalized.
2. Wrong: i asked uncle chris if he knew the best places to eat near tulane university.
Better: I asked Uncle Chris if he knew the best places to eat near Tulane University.
Explanation: The first letter in the sentence, the name (including its title), and the proper noun/name of a college need to be capitalized.
3. Wrong: the captain came on the loudspeaker to announce that the great green wave would dock soon.
Better: The captain came on the loudspeaker to announce that the Great Green Wave would dock soon.
Explanation: The first word in the sentence and the name of the ship need to be capitalized. The word "captain" is not capitalized here because it's a title without a name.