You know, I never really noticed this thread before but I started teaching my 'friend' Japanese and it's pretty hard. It's hard to judge the best order to teach things in and how to keep retention. I do weekly tests before each new lesson that reviews everything learned until now, and I throw in like 5-10 new kanji per week. But I'm not sure about how things will work out in the long term. She'd already taken a year of Japanese, so she has enough of a background that we were able to jump into things, but dunno!
The order I've tried teaching it is:
1. Verbs (all 3 groups)
-Plain positive/negative
-Polite positive/negative
-Past (plain/polite; positive/negative)
-Te/~naide form
-Teiru form
-Te Kudasai/Kure
2. Adjectives
-Past tense conjugation
3. Numbers/Time/de/e/wo/ga/ni particles
4. To omou / To iu
That's sorta what we've covered so far. I'm planning on doing the:
-Potential ~eru, ~rareru
-If/Then ~ba / ~nara
-~kutemo
-Passive
Basically one way I've tried to figure out what to teach is after the basics are covered, we translate a j-rock song each time and any new grammar points that are in it I teach.
The approach I'm going for is purely to master all the grammar points ASAP and pick up a bunch of kanji, because once you have the grammar down you can just pop words into a dictionary if you don't know them and be able to translate the sentence. Grammar first, vocab later.
Hope it works! I'd like to help her be semi-fluent to at least make it around Japan fine, read easy manga, watch anime raw, listen to j-rock and be able to understand the lyrics, etc...by the end of the year. It took me about 3 years to get to that level, but I'm hoping with a 1 on 1 private lesson tailored to just the one person it'll go much faster.