Some of the difficult parts of the French grammar :
- past participles conjugation changes depending on where they are related to the verb.
J'ai vu les feuilles dans l'arbre
Les feuilles que j'ai vues dans l'arbre
Many French people do mistakes here!
- for English speakers, one of the biggest problems is that in French, like most of the other romance languages, there is no neutral gender; everything, and I mean everything: people, things, animals, ... is either masculine or feminine. Some examples:
a table -> une table (feminine)
a board -> un tableau (masculine)
a horse -> un cheval (masculine)
a cow -> une vache (feminine)
a cat -> un chat (masculine)
a goat -> une chèvre (feminine)
From the words above, you could conclude that words ending with 'e' are feminine. While it's true for a lot of them, it's not always the case:
a poem -> un poème (masculine)
a tree -> un arbre (masculine)
- the letter 'e' can take different accents: é, è, ê, e, each with a different pronunciation
- English uses a lot of passive phrases ; French tends to use mainly active ones.
I'd say that knowing intermediate Spanish will definitely help. Grammars are very similar (I'm a beginner in Spanish). However contrary to Spanish the pronunciation far less consistent.