Rough guidelines for written documents in the future: https://writingcenter.fas.harvard.edu/pages/strategies-essay-writing
Additional note: Though not mentioned in the above link, it is common to avoid contractions in formal English writing (instead of "it's", write "it is"), https://www.aje.com/en/arc/editing-tip-contractions/
Quotation: Harvard Style as described in PDF:
→ Writing Style: American English