1. The first word in a sentence. You should always capitalize the first word in a sentence regardless of what type of word it is.
2. Proper nouns (names). These include the names of people, locations, places, days and months, companies, etc. For example: Matthew, Helen, France, Tokyo, Mississippi, Microsoft, Saturday, January…
3. Honorifics and titles, as well as their abbreviations. Mr., Mrs., Ms., Miss, Doctor (Dr.), President, Lord, etc.