Learn Beginners Spanish
The hardest part of reaching any goal is actually starting. This is especially true of learning a language on your own. After all, how are you to go about learning without the structure that a classroom environment provides? The solution to this problem will depend heavily on which language you are learning. For many more obscure languages, there may be no coherent beginning-to-end program. Fortunately, there is a large market for Spanish-learning materials these days and so exist several companies offering a range of more-or-less complete Spanish learning packages. You simply purchase the program, most of them sliced into several different segments, and go from the first page to the last. As far as I'm concerned, you only need to consider 2 alternatives: the renowned Pimsleur program or the equally famous FSI Spanish program. Both are excellent and proven effective and both come with roughly 15 hours of audio material, which is CRUCIAL if you ever want to speak and be able to understand the language. You can NOT learn to speak Spanish without hearing it, so the more tapes the better.
The Pimsleur Program
Pimsleur is far more effective and easy to use but it also carries a much higher price tag (about $217 for each of 3 volumes!) but if you can afford it, I HIGHLY recommend that you buy it. Each level of Pimsleur comes with 30 all-audio 30-minute lessons. You simply do 1 lesson a day (you might want to do each lesson twice a day, actually) and in 30 days you will be amazed at how far you've come. The best part is, this is a program that is ideal for use during your daily commute (30 minutes to and 30 minutes from work). And I'm not the only one singing its praises: check out the Pimsleur user reviews on Amazon.com. The only catch is that you can't just do the 1st level by itself. You really do need to do all 3 levels to get the full benefit. But at the end of the program, you will speak quickly and clearly at a reasonably advanced level and what's more, you will actually be able to understand what people are saying to you. Even at $600+ for the whole package, I strongly believe this is the best-value for your money (just think of how many $300 college classes you would have to take to reach the same proficiency, and that would take 3-4 YEARS instead of 3-4 MONTHS). You can buy it directly from the publisher, but you will save money on Amazon.
The Foreign Service Institute (FSI) is the branch of the U.S. government that specializes in training all U.S. diplomats and foreign service personnel. A major chunk of its responsibilities involves the teaching of foreign languages to the U.S. diplomatic corp. Because of the sheer number of students and different languages it was tasked with teaching, the FSI developed a rigorous, efficient, and highly practical method of language-teaching that did not necessitate the presence of expensive (and scarce) teachers of the language during much of the learning process. This program, developed in the 1950s but still every bit as good, is now available to the general public for purchase from the FSI itself (good luck wading through that bureaucracy) or through several commercial publishers. My personal favorite is the Barron's Mastering Spanish Series, which comes in 2 volumes (at about $50 each). You might also consider an updated (though in my opinion slightly inferior) version of this course called Platiquemos, which is broken up into 9 volumes (at $99 each). However, I do not feel the marginal advantage of a somewhat updated vocabulary (the word for "mother" and the verb conjugations haven't changed!) is worth the significant price increase. Each volume of Barron's Mastering Spanish will run you about $50, which is a lot nicer on your wallet than Pimsleur. The downside of this method is that it cannot be done without the book, which means no rush hour-learning. However, it can be every bit as effective as Pimsleur if used properly.
Time to Begin
At this point, you should simply start at the beginning of either Pimsleur I or Barron's Mastering Spanish I, depending on which you've chosen. For Pimsleur, do each 30-minute lesson twice a day with perhaps a few of the more difficult lessons requiring 3 times. For Barron's, you should work about an hour a day with the book and tapes. After you've gone through a unit once, you should be able to do it without the book using just the audio. The best would be to redo the previous night's material aurally on your way to work in the morning. It is important that you COMPLETELY master all of the material in each section before moving on or you will regret it later. It should take you between 1 and 2 months to complete the first level of your chosen program. By this time, you should know basic vocabulary, grammar, and be able to make polite small talk. You should also be able to express yourself in both the past and present.
Additional Beginners Tools
Ideally, you should be supplementing your early studies with some vocabulary drills. Since about 85% of everyday speech uses just 1000 of the most common words in Spanish, it is easy to see why this is important. The best way to do this is with flash cards because you can carry them with you anywhere and use idle minutes to learn a few new words. You can buy a pack of 1000 Spanish flash cards from Amazon for $12.95, which is a pretty good deal if you don't want to spend hours making your own. You could also purchase a little book called 1001 Most Used Spanish Words by Seymour Resnick. At only $2, you can't go wrong! If you're really set on learning vocabulary in your car, you could try out the all-audio Vocabulearn series (3 levels but with literally thousands of words and phrases) for about $38 total. I haven't used Vocabulearn but people who have seem to like it. Strive to learn 10-20 vocabulary words per day at a minimum no matter which method you use. Keep in mind that many of the words on your vocabulary list will also appear in your chosen program, so that will help make the task of memorizing them easier.
In addition to vocabulary, you might want a bit more grammar than either Pimsleur or FSI provides at this point. I recommend Essential Spanish Grammar by Seymour Resnick, which is only 115 pages long and costs a mere $5.95. You might also want to check out Practical Spanish Grammar by Marcial Prado, which is a decent workbook for this level at about $13. My in-depth reviews of all resources mentioned on this site are contained on my Spanish Learning Tools page.
After you've finished the 1st level of Pimsleur or FSI, learned a bit of grammar and about 1000 vocabulary words, it's time to move on to Intermediate Spanish.