[Haskell-beginners] f . g or f g or f $ g?

Hello all I frequently get confused over f . g vs f g. I do understand the following With: g :: a->b f :: b ->c f.g :: a->c However f g is a type error, because then f would have to accept a function (a->b) as its first parameter, but it only accepts a b. Is there a way to easily remember when to use f.g and when to use f g without having to do this type algebra. -- Martin