Knowing fundamentals of the grammar early helps immensely. Not learning them fully, but at least being aware of them. E.g. the fact that there are 4 verbs mood

Knowing fundamentals of the grammar early helps immensely. Not learning them fully, but at least being aware of them. E.g. the fact that there are 4 verbs moods in French - indicatif, subjonctif, conditionel and imperatif - is usually explained few weeks, if not months, into learning the language. Having been through this, I would've much prefered this to be mentioned right away, because it greatly helps with making sense out of written text. I am a computer programmer however, so it might not apply to everyone. Ditto goes for verb conjugation comprising two distinct classes - regular and compound. Trivial to explain, yet it's inevitably smeared across several weeks, confusing the heckout of the otherwise trivial subject. Another e.g., also from French, its alien-structured use of pronoms. This too IMO needs to be explained in first few days into the language. Yes, you can go by example here, but a single hour of explaining this will greatly simplify groking of all the examples that will follow.