Tips to learn Spanish
I was born in Argentina and lived there for 30 years. I can say I am an native Spanish speaker. I moved to the States at the age of 31 with very little knowledge of English. After 10 years I can say I have experienced the process of learning a new language with very little, almost no formal education. Here are some of my tips that you can certainly use to learn Spanish as well.
Push yourself to watch TV in Spanish (use subtitles in Spanish instead of English)
Always use a Spanish dictionary to look up words you don't know, reading the meaning will increase your vocabulary and will provide more interpretations of the word.
Create a group of friends or go to places where you will be pushed to listen and speak in Spanish.
Don't be afraid to make mistakes.
To improve your vocabulary read articles of your interest in Spanish on line.
To improve your listening watch TV en Español.
Please share in this thread more experiences about learning Spanish or any other language. Feel free to ask questions and of course revise my own English. 
I will add more tips as soon as I can think of them.
Note: I highlighted all the tips in this thread for easy reading since there are many comments and opinions that are specifically tips to learn Spanish. Also I have removed highlight from topics don't represent tips.
31 Answers
Translation to obtain writing skills.
The real challenge is not to translate a text in Spanish to your own language, because you know already how to write in English, the challenge is to translate an English text into Spanish. That will help you to develop writing skills in Spanish.
Translating to understand. When you need to learn comprehension you can read a text in Spanish and then create questions or develop more of the theme in Spanish. Translating it to English only will improve you English writing skills but limit your understanding of the foreign language to a higher level.
Try making your shopping list in Spanish.
Watch children programs, read children books
Besides just watching children's programs or reading children's books,
I have found it helpful to also write out short book reports once I have read the book, or if I am feeling extremely ambitious, I might try to make a short oral summary of what I just watched or read.
I am so glad you started this thread Juluqe. After you gave all of the help on the "medical emergencies" thread yesterday, I was wondering if Spanish was your native tongue. Now it is good to know. We can always use help here with all of the mistakes we make. I am one of the biggest contributers of mistakes. 
I love your advice, especially since you are speaking from experience.
I have recently started listening to videos (that are free!) which have been extremely helpful. They suggest that people shouldn't spend all of their time memorizing rules and conjugation tables. Instead, we should listen to the rhythm of Spanish speaking people and focus on the sounds "like a child would". It was also suggested that in order to internalize the language, we should learn about things that are important to our own daily lives (vocabulary and phrases, etc).
I have found that to be true when visiting Spanish speaking countries. Because I have to quickly learn certain words and phrases for survival, they have become important to me. I have absolutely no problem remembering those things I have learned in Latin America. I do have more difficulty remembering many of the words I study off of the endless "lists".
How do you feel about this advice?
I've recently moved to Spain with very little knowledge of Spanish and i must say the tips you give are very good ones 
This tip i'm gonna say will probably sound very funny to many of you
Watch children programs, read children books, etc..
The level of Spanish in those is very good to start with. To form basic sentences and visualise the words.
Try avoiding literal translation in your head. Try learning by phrases rather than by words.
Listen to Spanish even if you don't understand 100%, be patient. You are learning even when you don't understand. Getting familiar with the sound of the language is very important to identify the words later.
Free places to listen native people speak in Spanish in USA:
Spanish Churches.
Spanish 12 steps meetings (AA, NA, OA ) they are usually open to anyone.
In this places you have the chance to interact as much or as little as you want. After the service or meeting, usually people are very welcoming and willing to listen. At the same time you may improve your spiritual condition. he he
Hola Juluque,
Excelente tus tips...Podrías hacer otro post pero pensando en los que quieren aprender o mejorar su inglés. Alguien podría pensar que es sólo cosa de cambiar en el presente artículo, donde dice Spanish por English, pero creo que mejor que suponer es recibir las opiniones directas de alguien que vivió directamente la experiencia de tener que aprender inglés desde cero...
Te felicito por tu excelente disposición para ayudar en este sitio.
Saludos
Carlos F.
Once you get past a beginner's level get a Spanish dictionary to use instead of a Spanish/English dictionary. Here's one that I have: Diccionario Larousse del español moderno
In addition to watching Spanish TV and, por supuesto, visiting spanishdict.com, try listening to Spanish songs.
Not only are they fabulous, you can listen to them any time via ipod, etc (while working out, driving, cooking, etc), and can look up the lyrics to check your understanding. I know for me Spanish songs have increased my knowledge of the language and have inspired me to keep learning - there are still so many things I have yet to comprehend! And although you may not understand everything, you can still gather the tone and overall feeling of the song, which will help to express its meaning. Personally, my favorite band is Mana. Their songs have two major themes: societal problems and love.
If you are a newbie at watching movies in Spanish, try watching Movies you watched before in English several times. So you can associate the story and what you remember of the dialogue with the the Spanish script.
When I go to a Mexican restaurant, I try to converse with the staff only in Spanish. They are usually pleased that I am trying and are happy to help me.
I listen to the Spanish sports radio station during my commute to work. I don´t understand most of the dialog, but every day I pick out one or two words that I do not understand then look up their meaning when I get to work. So every day I understand a little bit more. It helps that they only talk about one thing: fútbol.
If one of the Spanish TV stations is playing a movie that I am familiar with and it has been dubbed in Spanish, then I watch it to see how much I can understand.
Pide a tu profesor que te dé las instrucciones de los ejercicios en español. Busca libros de español con intrucciones en español. That will increase your need for learning Spanish.
