I saw my wife's profile on a website (amigos.com) when I went looking to find a Mexicana who lived nearby. As luck would have it, I saw her and even though she spoke no English (and still doesn't) and I knew no Spanish, I decided to start communicating with her using a dictionary and the internet translators. We progressed to chatting on Yahoo and my written Spanish progressed rapidly. It took some time being with her for my oral Spanish skills to catch up to my written Spanish, for a while I had to almost visualize writing the words out.

Essentially my Spanish progressed as though I were a child learning to speak. At first I had to say everything in the present tense but I was concentrating on building a big enough vocabulary to say almost anything I wanted. Later I began using the preterite and future tenses. After I mastered those I began using the other tenses. I still have a little trouble with the subjunctive which is used far more in Spanish than it is in English.

I grew up in Montreal and know how to speak French but I found French almost more of a hindrance than a help in learning Spanish. Even though they are both Latin languages, I do not find many similarities.

Traveled extensively through Mexico during my 'wild days'.

Worked on an advanced degree at UNAM - Universidad Nacional Autonoma de Mexico, Mexico City (alas, the necessity of returning to the US to earn a living kept me from finishing).

Taught Spanish in HS.

Taught Spanish in a community college (except in those days, they were referred to as 'junior colleges').

Worked as a bi-lingual aide for the State Department 2 years during the Mariel Boat Lift.

Married to a Costa Rican for 16 years, although she spoke perfect English (and French and Portuguese, too, for what it's worth) by the time I met her.

Married to a Calena about a year and a half now (and she DOESN'T speak English---guess I really should get around to teaching her one day).

Live in Dallas, which (at least in certain parts) is practically becoming a colony of Mexico anyway.

Watching TV and listening to the radio are also good methods, and here in Dallas we also have a rather prolific Spanish press, two or three dailies and I can't even remember how many weeklies and ‘neighborhood shopper’ or its equivalent in Spanish.

Despite all this, every day my wife manages to use at least 3 words that I don't know, ha ha. (Colombian Spanish is different from Mexican Spanish, a good analogy would be one of us speaking with somebody from Australia—and don’t get me started on Cubans, even other native Spanish speakers have trouble understanding them).

For those who have good spanish skills and grammer, try 1001 pitfalls in spanish.  It has lots of good tips and refresher points.  I learned about estoy para with an infinitive, for example.