I mostly use English or Filipino in my everyday interactions, but I've been studying Chinese, Japanese and Korean for a long time now (about a decade or so).
As of now, I can read and listen to 8 languages in varying degrees of understanding, but I can only speak three of them comfortably.
I usually learn grammar and basic vocabulary (via books, websites, flashcards, etc.), then I immerse myself in content in that language exclusively, consulting a dictionary, machine translation, or language forums when I find myself struggling to keep up.
But the number one rule is: avoid falling back on your mother tongue as much as you can! the less you rely on translations, the easier it will be acquiring new knowledge later on, even if it's a really steep cliff to climb at first.
