How to Learn German from a Native Speaker Whos Never Taught?
I would definitely recommend 501 German Verbs for the most common verbs and their conjugations. Practice, practice, practice those irregular verbs. Association is a good memory technique. You’ll need it to learn the gender of various nouns. Further, depending on the gender you use (say, Schild) the noun can take on different meaning (say, a license plate versus a medieval shield). Grammatical usage of German can change depending on whether you are writing a sentence or speaking it in conversation. Textbook work won’t help you here as much as practicing with your friend. Using conjunctions can be mostly idiomatic, and unusual conjunctions can be tied to certain verbs to impart a specific meaning. Learning these will come down to practice. Good luck! German’s a beautiful tongue.
I don’t know about learning from a friend, but I am currently taking a class at a local language school with an instructor. The textbook they have us using is Ultimate German: Basic-Intermediate Coursebook by Living Language. There is also an edition that comes with a follow-along CD. The book focuses equally on grammar and vocabulary, which I like. It’s been pretty helpful for me as I am good with the vocab but get stuck on the proper grammar. I second the notion of watching lots and lots of German films (oh, there are so many good ones!) as this is where I’ve learned most of my vocabulary from and is an excellent next-best option when you don’t have any German friends to talk to. It’s so important to hear the language spoken in a natural context, outside of learning tapes and CDs which are geared towards beginners and therefore speak uber-slow and clearly, unlike real life.