Thank you for your recollection. It is very helpful to understand what approaches are particularly appreciated. I must add that the "best" approach is very subjective - for example if a student had learned another language in the past using a particular approach and was successful with it, he/she might follow the same approach again.
I learned English by studying its grammar (at school), and when last year I started taking private German classes with a rather informal approach I was quickly overwhelmed and full of doubts - I couldn't figure out a rule on my own. On another side, my husband, who studied languages in school but most of his foreign languages knowledge come from his past as a sales representative around the world, was extremely enthusiastic of this informal approach and was picking up very quickly. The more he felt confident in German, the more I felt behind. Can I say I am scared by German now? He can't wait to resume classes and I can't wait to find an excuse not to. B)
As a teacher, the hardest part for me would be to teach how to pronounce letters and sounds in an acceptable way, how to explain where the tongue is, how to put your teeth and lips, etc. (children and some lucky people figure out this naturally, but most adults usually don't). I have met native English speakers who are fluent in Spanish after living here for a very long time, but with a terrible pronunciation - I think the letter that really gives away a native English speaker is the "r": you can't speak Spanish like a train and then say -rr- in parrilla the same way you pronounce arrive it is really a pity after so much effort on the grammar and the vocabulary!