When do you leave it out? X
When do you NOT use an article? When you talk about:
1. Members of a group/country
(Americans always eat a lot of junkfood/French people refuse to speak English)
2. When a sentence starts with 'most/all and both'
(both students were named student of the week/Most teachers hate grading tests)
3. Special titles or functions
(He is President of the USA/She is prime minister)
4. Streetnames/lakes/buildings like schools or hospitals)
Niftarlake College is based in Maarssen/Lake Loch Ness is surrounded by mystery/