Language learning in general is a subject I am very interested in, as much as, if not more than, grappling. I'm not an expert on Portuguese though.
My, er, two centavos.
Start with a basic course that has lots of audio. If you rush into reading and writing, your pronunciation is going to suck horribly.
Pimsleur is a good in that it's audio and it will help you pick up correct pronunciation from native speakers. It will NOT give you a good understanding of grammar or bring you anywhere close to fluency but it is vital that you don't start off with a horrible English accent. I have listened to all the Pimsleur Portuguese courses - it's easy to do when washing up, jogging, catching the train etc. I DON'T recommend buying the Pimsleur courses but if you can get hold of them, they're a good start. My local library seems to stock pretty much all the Pimsleur courses.
A guy called Michel Thomas did some really excellent courses in French, German, Italian and Spanish. His associates produced courses for other languages using his method. They're not as good as the originals, which in my opinion were AMAZING, but they are good. There's a basic course and and advanced course and you'll need both. I have done the basic Portuguese course but not the advanced. However, I have done the French, Spanish, German and Italian courses and the format is pretty similar. They WON"T give you much vocab but they'll give you a GREAT understanding of the verbs which is crucial. It's quite a different approach to Pimsleur. LOVE these courses. Michel Thomas was the man.
FSI is available for free on the net and as far as I know is legal! On the downside, it's pretty heavy going, it seems to be designed for would-be diplomats studying all day every day and it certainly ain't pretty. However, I've heard a lot of good things about the course. You should be able to download the course here.
FSI Language Courses - Portuguese
I don't have much experience with Rosetta, Assimil, Teach Yourself etc. There are a myriad of courses out there. As I said, the important thing is to start off with plenty of listening so that you don't mangle the pronunciation too badly.
Once you get started on a course I recommend that you start using an SRS program like Mnemosyne or Anki. These are flashcard programs that test you on vocabulary or whatever you want to learn. I mostly use Mnemosyne because of its simplicity but I believe Anki is actually a more powerful and versatile program. I have both loaded onto a USB stick so I can practice anywhere I have access to a computer.
Spaced repetition - Wikipedia, the free encyclopedia
Welcome to the Mnemosyne Project | The Mnemosyne Project
Anki - friendly, intelligent flashcards
You can download pre-made decks or make your own. It's up to you.
So, say you were doing Pimsleur, you might want to put the sentences you feel are useful into your SRS and review them until you know them. Of course, you are not limited to that and you can grab sentences from wherever. A word of warning, it's not wise to overdo it with SRS - limit yourself to about 10 new sentences per day or you might burnout. I usually do about 250 cards per day on these programs.
There are Pimsleur Portuguese transcripts out there on the net - they're not easy to find though.
Once you've reached a certain level, i.e. completed a couple of basic courses, got a few hundred sentences in your SRS program, I think it's best to start tackling Portuguese audiobooks and parallel texts. I use audiobooks by reading the English version of a book, say, something by Dan Brown, while listening to the language I want to learn. You are not going to understand everything but it does wonders for your listening comprehension and helps to reinforce what you know.
If you can get hold of a parallel text with audio, this is ideal! You can do what I described above whilst checking unknown words against the Portuguese.
If you just have a parallel text, well, that's a good way to study but beware of ingraining bad habits regarding pronunciation. For the last time, it's REALLY important.
After you've done a few books, it's really time to hunt down a conversation partner. There's plenty of places to find language exchange partners on the net. You want someone helpful who will give you feedback on your mistakes and not just try and speak in English. Avoid language leeches like this like you would grappling partners with ringworm! Oh, and you don't need to pay people to teach you! It's absolutely unnecessary when there's so many people out there who want to learn English.
Other good websites:
Language Learning Forum
(This is like the Sherdog of Language forums)
All Japanese All The Time Dot Com: How to learn Japanese. On your own, having fun and to fluency. About
(Has really good advice concerning how to approach language study)
Things I do NOT do while learning languages: anything boring, read books aimed at young children, spend ages looking at dictionaries (I hate dictionaries)...
I hope this has given you some ideas! The key thing to learning any language on your own is resources. Fortunately, the net is full of great stuff.
Anyone who's learning or interested in learning Japanese, Spanish, Italian, French or Portuguese, what the hell, even Korean, feel free to PM me.