Thomas_

I've been teaching myself Japanese too. It's funny, I've made the exact same experiences as Pistolen08.

Rosetta Stone sucks. It's boring, doesn't teach you anything except for some vocabulary, doesn't have good exercises, etc. Waste of time.
Pimsleur and most other Audio Programs suck as well. They're boring and if you don't listen to the same lessons many times you won't remember anything. At least it's like that for me, if you're more of an auditory learner it might fit you well.

My suggestions:
- Books. I don't know the book Pistolen08 suggested, but I highly recommend "Japanese from Zero" (1-3). You don't need any previous knowledge for this book. Look it up on Amazon. Also very good are the flashcards for Kanji and Kana, also to be found on Amazon.
- Podcasts. I like listening to podcasts on my way to College. I recommend japanesepod101.com. Register and pay one time, download all the episodes, cancel subscription ; )
- Japanese friends or people on Skype. Well, I have a Japanese girlfriend and many Japanese friends so I don't need to talk to people on Skype, but finding Japanese people might not be that easy if you're not living in CA or HI... I also used the Skype method Pistolen08 suggested for other languages I was learning some time ago and I highly recommend it. Another site to find language exchange partners is mylanguageexchange.com, or just start writing to random people on skype search : )

naturefreak525

I'm in college right now. I've been studying German since middle school and French since freshman year of high school. My Vietnamese, I think , has actually gotten a little better now that I'm away from home. I think it's because I don't want my roommate or some people to understand what I'm saying sometimes so it makes me work harder to try to get things across clearly. That could be a good reason for you to tell your mom, if you like. haha.

mikemac

take a look at the Language Learning Forum website. It is specifically for people learning on their own.

Pistolen08

I also recommend a program called "Anki". It's a flashcard program that can be used to learn kanji+vocab etc...
SourceForge.net: Anki

I would also suggest the textbook series "Genki" if you want to use the books that colleges use. They can be a little pricey, but some people swear by them.

I wouldn't try to learn from watching anime, because a lot of fansubbers suck at translating. Stick with the proven methods. The only real way to become fluent is to go to Japan and converse with natives though. Good luck!

Coño

Experienced language learner here.

I also picked up Spanish from my parents, but it was also a pretty low level.

I ended up teaching myself, as well as learning Portuguese.

My experiences:

Rosetta Stone - horrible program. Just not worth it at all unless you can get it for super cheap (under $100, and that's pushing it)

Pimsleur - it's good, but horribly overpriced for its quality. You don't learn very many words, but it's a decent foundation until you get into more advanced things.

I want to point you to probably some of the greatest resources for language learners:

Language Learning Forum

Amazing language learning forum; there's a hyperglot professor there (speaks many languages, very intelligent guy) that writes a ton on the forum, answers questions, shares his experiences, etc. Everyone there is a language enthusiast, and happy to help. It's decently active, but it has room to improve in that area.

And finally, the language programs I think you SHOULD be using:

FSI Language Courses

These are great courses, used by the Foreign Service Institute which intensively trains their diplomats in the language for so many months before sending them off to do the job that they need to do.

They're pretty old (but still great) and part of the public domain now, so they're absolutely free and legal from this site. However, not all programs are available on there, some are incomplete, etc.

Vietnamese unfortunately isn't available there, but these programs can also be purchased completely remastered with a physical booklet and CDs instead of reading a PDF and MP3s on the computer. They're pretty expensive though; look into Barrons FSI (I think that's the product).

Chinese has a ton there, however what they have isn't on par with their other programs such as Spanish.

If you have any questions, let me know.