How to Study Haggai
Read through the book of Haggai once, and then read it again and mark in a distinctive color every occurrence of the word people (the people in general), including the appropriate pronouns. Also, mark every reference to the house of the Lord, also called the temple.
Having done that, did you notice a pattern to the book of Haggai? Read through the text again and mark with the symbol of a clock ¹ every reference to specific dates as seen in 1:1, 15 and 2:1, 10, 20. The sacred portion of the Jewish calendar can help you see the "when" of the message.
Now read Haggai again and, in a distinctive way, mark every occurrence of the phrases the word of the Lord came by the prophet Haggai, the word of the Lord came by Haggai the prophet, and Haggai, the messenger of the Lord spoke by commission of the Lord. When you finish, you will see that Haggai is a series of messages.
Now read Haggai, one message at a time.
As you do, mark the key words: people, the house of the Lord (temple), Lord of hosts, consider and shake; along with their synonyms and pronouns.
5. Complete the Haggai Structure.
Key Words in the NIV and KJV
Key doctrines in Haggai
God's presence in the temple (1:7, 8; 2:7-9; 1Kin 8:10, 11; 2Chr 5:13, 14; Ezek 43:5; 1Cor 6:19, 20; 2Cor 6:16-18; Rev 21:22; 22:1-21)
Obedience by the people who teared God (1:12-15; Deut 11:8; 1Chr 24:19; 2Chr 19:9; Ezra 5:2; Prov 15:33; Col 2:6, 7; 3:22)