When not to use an article:

To indicate a profession Il est docteur. He is a doctor.
Elle est avocate. She is a lawyer
Il est devenu infirmier. he became a nurse.
Elle est devenue mère au foyer. She became a stay-at-home mom.
After de, if the noun is plural and/or references a quantity. Il a beacoup de problèmes. résoudre d’une problème. ( Article … cuz no quantity reference) He has alot of problems. solution of a problem
Elle a reçu plusieurs invitations. She got several invitations.
After some prepositions when talking in a general way
avec -with Elle cherche un appartement avec balcon. She is looking for an apartment with a balcony.
sans-without Tu ne te sentiras pas mieux sans étirements. You won’t feel better without stretching.
sous- under L’Europe est sous eau. le chat est sous table. Europe is under water.
en - in …. Nous sommes en classe. We are in class.
par- by Il fait ça par habitude. He does that by habit.
After “ne… ni… ni…’’ - neither - nor Je n’ai ni stylo ni cahier. I have neither pen nor notebook.
After parler when talking about languages (optional) Je parle français depuis plusieurs/quelques années. I have been speaking French for a few years.
Il aimerait parler espagnol. He would like to speak Spanish.
Before meals (sometimes) Nous avons pris dîner à 19h. We had dinner at 7 p.m.

partitive articles become — de before adjectives — des films — de bons films