Jacqui, do you mean when to use du or de?
There are many different scenarios .
1. the basic rule is that you use "de"after expressions of quantity: beaucoup de pain, peu de travail, trop de bruit, assez de couleurs etc.
2. le partitif du, de la, de l', des (+) // de (-) : some//any
* du= contraction of de+ le => you need to know the gender of the noun . In this case "de"is the "partitif", describing "some " of something. ex: j'ai du pain (I have some bread, or I have bread)
* In the negatif du becomes de: Je n'ai pas de pain. (I don't have any bread/ I have no bread)
* with a feminin noun there is no contraction: j'ai de la soupe//négatif: je n'ai pas de soupe.
* in the plural: the contraction is des (= de+les=>des). J'ai des cousins // je n'ai pas de cousins
Remember that you need to know the gender of the noun. Mistakes are to be expected, ask the children to be lenient!
PLease let me know if this is what you needed to know. This is a good topic for the mini-lesson on my website, www.cevenneslangues.com perhaps next month.
Bonne chance avec de, du, de la...et bonne année.
Note in reply to Dedene: you can say "le pain"of course: "Tu peux me passer le pain?" Vous avez apporté le pain? "It is more specific because le is the definite article. Le linge is feminin however. ex: "Tu as rangé le linge? "
Again, there many different scenarios so if you need more examples let me know.