Learning two languages at once?

I want to expand upon the topic of language learning, inspired yet again by fluentin3months.com, this time by a specific post 'Learning Two Languages at Once: Can You Learn Multiple Languages at the Same Time?'

For a period of about one year I was learning German, progressing from beginner to intermediate, at the same time as beginning from scratch with the Croatian language. I've been living in Hamburg, Germany for three years now and wanted to learn the language for obvious reasons; to communicate and connect better with friends, colleagues, and everyday people. My girlfriend is from Croatia, so in part because of raw curiosity, but also to gain the ability to communicate with her family and friends, I started to learn from zero.

German had gone quite well even without an official course, mostly because I live in Germany and had a support structure to give me the opportunity to practice. Also, I was quite motivated so my self-study worked. Croatian on the other hand floundered for months, and is still only progressing slowly since I have time for only one one-hour long Skype course per week. Still, I feel like I really learned something for that period of time where I was learning two languages at once. I am heading in to a period where I will probably need to draw on these skills again. I am moving to Paris, France, and will probably want to pick up at least basic French and at least slowly continue with Croatian, albeit both with less urgency than before.

The article, written by Benny Lewis, the founder of the site, lists five things that I could not agree with more:

1. Choose languages that are really different
2. Study both languages each day
3. Avoid multi-tasking
4. Give each language a unique study routine
5. Don't rush!

These are absolute gold, and took me months to figure out myself. The most important I found was to really practically separate the way that you study each language. Don't study them in the same place, or at the same time of day. For the period I was studying German and Croatian I only studied German in the mornings before work, and only studied Croatian in the evenings after work. One example was listening to a German podcast on the way to work (Echo des Tages from NDR), and a Croatian one on the way home (actually from Serbia because there are no Croatian pods available, Srbija u dva). I would have loved to study each every day, but didn't have the discipline to do so, even for a small amount of time.

I hope this is useful. Just like Benny says, it is probably not possible or recommendable to try to become fluent in two languages at once, and it's also hard to imagine that being necessary for many people. But brushing up or slowly improving skills in two languages at once is something that many people probably wish they could do. It is definitely possible, just try to set these guidelines first so the time is well spent.