Multiple languages at once
Is it good to learn multiple languages at once? Or would it be better to learn a secondary language and then learn other languages based off of that second language. (English -> Spanish) (Spanish -> Italian; Spanish -> French)
Personally (And note, this is ONLY personally. I do not have a linguistics degree), I like to learn languages from completely different families. For instance, I've been learning Spanish since the 6th grade, and have been learning German for 2 or 3 months now. I never get them confused. Being european languages, they share a few similar words here and there, but they're different enough where I don't ever accidentally say a german word instead of a spanish (or vice versa). I plan next to study a Slavic language. I've always had a hard time getting comfortable with romance languages after learning Spanish, due to the extreme similarities in some areas, and subtle differences in others.
Now, (personally) Russian is almost like a Slavic Spanish! Very similar vocabulary and basic grammar structure. And, I don't have too many problems with Russian, due to knowing Spanish beforehand (and not even fluent)... so, that seems to help immensely with vocabulary and certain aspects of grammar as you learn both languages. :)
If you're aiming to become fluent and fully master a language, I think focusing on one at a time would be much more efficient because then you'd have so much more time to concentrate on that one set of grammar rules, vocabulary, and pronunciation, and learn to "think" in that language. Also if you're learning similar languages like Italian and Spanish at once, then you'd probably be mixing up a lot of words and rules. And it really depends on the language- for example, learning French in school has really helped me with Spanish (especially conjugations). But a lot of people say that knowing Russian has helped them with Spanish; being a native speaker, I can't say that it's helped me more than with remembering the Spanish word for wine. So I guess it depends on the person :)