Mistakes will always be made in French, and now you can learn from them.
Wrong: Beaucoup des
Right: Beaucoup de
Explanation: Beaucoup des is not always wrong - just most of the time. Like other adverbs of quantity, beaucoup is nearly always followed by de, with no article:
J'ai beaucoup de temps
I have a lot of time
Tu as beaucoup d'amis
You have many friends
C'est un détail de peu d'importance
It's a minor detail, a detail of little importance
In the above examples, the nouns are unspecific - they refer to time, friends, and importance in general. The only time beaucoup de and the other adverbs of quantity can be followed by a definite article is when they are referring to something specific, as in these examples:
J'ai acheté une chemise dont beaucoup des boutons s'étaient détachés
I bought a shirt that a lot of the buttons had come off of
(I'm talking about the specific buttons on this particular shirt)
Beaucoup des idées de Jean-Luc sont intéressantes
A lot of Jean-Luc's ideas are interesting
(I'm not referring to ideas in general, but rather the specific ideas that Jean-Luc has)
In most cases, if you can translate the French as "a lot of the" + noun or "a lot of ___'s" + noun, you use the definite article. Otherwise, if you only say "a lot of" + noun in English, just use de. (There are undoubtedly exceptions to this rule, but it should help you in most cases.)
Related lessons:
* Adverbs of quantity
* Definite article
* De vs du, de la, des

