What do you think is the simplest, yet most effective way to learn Spanish?

I did that while living in the US. Had a friend from Cuba who was much happier speaking Spanish with her friends and family. We hung out a lot together. That's really how I became conversant. We went to Uruguay for a month, stayed with her girlfriend's family, no English the whole time. Amazing experiences.

 

Si, Y por supuesto en el sur de Florida, Miami, where I grew up.

 

Spanglish is a type of artform.
For me it was mostly for fun, to see how creative interactions could be. But it is also a learning and teaching tool, as odd as that might initially seem.

 

I think the most effective way to learn any language is to throw yourself into the water and go live in the middle of it.

There always comes a time where the brain eventually does the switch and starts adapting towards what is being spoken around you.

 

My first course of action was to study books, learning how all the parts of speech work and applied differently in each language. A chart of all verb tenses depicting meaning and showing how each is formed from all three roots was immensely useful and I memorized that over a course of time. Lastly, collect vocabulary words and go around thinking in my mind what things I saw were called and how I might converse about them. So a good year learning about the mechanics without interacting with a native speaker. Then it was listen to music and comedians, and try to understand the radio. I'd record and replay, writing what I heard until it got easier to figure out. Finally it was look for native speakers and get embarrassed trying to understand and formulating a coherent thought in words. Read books and look up every tenth word. Then practice for fifty years. Now I can converse well, read, write, watch movies and YouTube adventures, etc. Por lo menos por ser gringo.