I've included useful resources below. I am not affiliated with any of them, but have found them very helpful for beginners and veterans alike!
The voice is both resilient and delicate - take a look a Mayo Clinic's guide to caring for your voice. If you want an in depth look at what physically happens when you sing, watch the Mayo Clinic's video "A Look Inside Your Voice."
Essentially, stay hydrated with non-caffeinated, non-alcoholic beverages and get plenty of sleep.
Find translations of song literature at The LiederNet Archive and arias at The Aria Database. After you're comfortable with the translation, The Diction Police can help you pronounce foreign languages with ease.
Want to learn everything there is to know about how music works? I highly recommend MusicTheory.net.