Tawianed, according to your profile, you are located in my favorite big city in Taiwan. My wife is from Tainan, so I've spent a lot of time there. They've got some of the best food on the island, IMO. They also have--by far--the best "Bing" shop (shaved ice with fruit) in Taiwan. It is the JiaNan Bing Guo Dian on NanMen Rd. I went there almost daily when I lived there in the 80s. And I make a point to go there at least once every time I visit Tainan.

Now to your question, the "painless" part of the equation requires a passion for learning Chinese. Without it, there will be some unavoidable pain. How do you get this passion? As some people suggested, finding a romantic interest certainly helps. But there are other ways.

For me, I first went to Taiwan as a Mormon missionary, so finding a romantic interest was strictly verboten. But I did quickly gain a passion for learning Chinese. I think that this came after I was successful in first gaining a basic understanding of simple conversation. This came from just talking with the locals a lot. As a missionary, this wasn't a problem. It's what I did 12-15 hours a day, everyday. There was a lot of trial and error, but I kept working on it. I was comfortably conversational after a couple months.

With a little success in my pocket, I was eager to learn more. And when I started studying the characters, my interest really piqued. And as I learned more and more characters, my conversational skills greatly increased. I think that you need to first get a basic knowledge of conversational Chinese before you can really start learning the Characters. But without learning the characters, your conversational Chinese will be limited.

So to start out, just talk in Chinese as much as you can. It takes some courage to try and fail, but keep doing it--a lot. Then, when you start to feel somewhat comfortable in conversation, hit the flash cards and start learning characters. Learn to write them too, if you can. It will help you memorize them. Get a local to teach you the basic stroke order rules for writing characters.

Since you are in Taiwan, learn the ZhuYin FuHao phonetic system (BoPoMoFo), and get some children's books with ZhuYin on the sides of the characters. For me, learning ZhuYin helped with my pronunciation more than any of the romanization systems.

This seems juvenile, but get a pen pal. Ask a local friend if they wouldn't mind swapping letters with you. And make sure the letters you write are hand-written, not on a computer. If your pen pal also writes hand-written letters, it will help you learn to read better than if you just read computer-generated type.

That's how I did it. Oh, and after my two-year mission service was up, I later returned to Taiwan, found a romantic interest and married her.