Online classes (1 on 1 or small group) by Skype using TPRS/CI methodology. If you don’t know what those are, a quick search on these forums will turn up a lot of posts discussing what it is and how it works. I’m a well-known trainer and presenter on Mandarin teaching methodology in the US, and have a number of readers available on Amazon (with recordings on iTunes as well).
Cost is NT$1200 per lesson via the Post Office in Taiwan, or US$50 by Paypal. 24 hours’ notice required for rescheduling a cancellation. The new schedule goes up at the end of the preceding month.
I primarily focus on beginners, but also take the odd intermediate level student. If you’re advanced, this method won’t have much that will benefit you more than getting a cheaper tutor or teacher on the ground in Taiwan. If you’re a beginner, and particularly if you’ve been frustrated with language school methods and memorization-based, “make a sentence” approaches, this way of acquiring the language can be enormously helpful.
Most common question is “how far can I get in [time period]?” I can’t say. But an average person will be through the same amount of grammar as is taught in the first 5 lessons of “Integrated Chinese” (a common college textbook in the US) in about 10 hours of class.
The other advantage of this method is – no homework. It’s best to read over your story (if you’re choosing to learn to read) or listen to the .mp3 recording you’ll get, but there’s not much in the line of memorization needed. Flashcards are available for use if you want them.
When I do a 30 minute session and then listen to the recording once or twice before the next session, I retain a lot more and feel more confident about what I heard in the lesson.