One difference between French and English that I'm a bit fuzzy about is when to pluralize attributes/possessions of individuals in a group. For example:
Les cochons fouillent avec leur groin. Pigs dig around with their snouts.
English pluralizes "snouts" but French keeps "groin" singular. Français Facile suggests that in French you generally use the singular when each individual in the group possesses one of the things, but it sounds like there's some wiggle room; I can't think of any examples off the top of my head, but I've definitely come across situations in French where I expected a singular but found a plural.
Are there any other rules/heuristics to know about?