Hi Matthew- 1) both are correct, although where I live (western USA), I would more likely hear: "I called you yesterday" 2) That is correct, although I would say "Please don't rush to a decision" 3) I would change the positioning of the words above and below in your sentence - for example "Please correct the information above and delete the information below." Basically, I moved the adjectives from in front of the noun to after the noun. 4) For your first sentence, add the verb is, in between Hong Kong and located - "Hong Kong is located in China." For the second sentence, I'm assuming Central is a neighborhood or district of Hong Kong, and in those cases, I would use in. "The headquarter of HSBC in Hong Kong is located on ABC street in Central." I would use the word at if Central was a specific place, for example "The headquarters of HSBC in Hong Kong is located on ABC street at the Central Market Place." 6) Most of the time, I would use the phrase "in your book", unless I was specifically writing something on the cover or on the outside of the book. I'm not sure about number 5, but hopefully that helps! Michael