I've been making slow but steady progress in learning Vietnamese. Some people have asked me how. My answer? Being lazy.
I'm lazy. I don't like to study on my own at home or listen to CDs and read along. I do have a tutor come to the office for 1 hour, four days a week. We just chat in Vietnamese. Other than that, though, I don't do any formal studying.
Instead, I insist everywhere I go that people speak to me in Vietnamese. When the waitress asks me "What would you like to drink?" in English, I always say "Tôi không hiểu tiếng Anh. Tôi hiểu tiếng Việt." (I don't understand English. I understand Vietnamese.) It's always a good joke, and it lets me practice saying everyday things like "I'd like a Coke with ice" as well as hearing Vietnamese spoken by native speakers. It's a little thing, but it does add up over time.
There are a few places where the staff speak to me only in Vietnamese now. A few weeks ago I had lunch with a Singaporean Vietnamese guy at one of these places. I was particularly proud when, as we were leaving, the waitress said "Goodbye" to him, but said "Hẹn gặp lại anh!" (see you again) to me. His Vietnamese is about a million times better than mine, but they knew he was Viet Kieu and defaulted to English. He remarked on it and we both had a good laugh.
No doubt my learning would accelerate if I actually studied. But as long as I'm making progress I'm happy.