1. What language is your native tongue, and were you lucky to be raised in a bilingual household?
Spanish, and yes, both my parents spoke English too (they spoke it when they wanted to discuss things they didn't want me and my brother to hear, but stopped when I started understanding them).

2. What other languages do you know other than your first language? If you care to explain, when and why did you learn them?
English, obviously (otherwise I wouldn't be posting this). I'd like to learn more, but for now that's the only other language I speak fluently. I started learning it at school, then took private lessons for about 11 years, and I'm still learning more by talking to English-speaking people, reading books in English, doing things online and watching movies, TV, etc.

3. Which language do you use most frequently, and which language do you prefer the most?
I use Spanish most frequently in my everyday life, and English online. I like Spanish better, but English has good things too, and I'll use the language that helps me communicate with my interlocutor, whichever it is.

4. What would you think of your vocabulary level? What is probably the most complex word you use on a daily basis?
I think it's quite good in Spanish, and decent in English. I'm still missing some everyday terms and expressions. I don't know what the most complex word I use on a regular basis is, maybe 'paradigms' or something computer-related. Yesterday I caught someone off-guard with the word 'heuristically', he had to look it up.

5. How's your handwriting? Is it legible, or do you think it's too sloppy?
It's clear and legible, provided you have good eyesight. It's neat, but tiny.

6. Do you happen to be a Grammar Nazi? Or are you fairly lenient on the grammar of others?
I make an effort to hold myself when I think my remarks about grammar are likely to hurt another person's sensitivity. I don't always manage it, but I can stop myself a lot more often than, say, when I was 12. Does that answer the question? In any case, I wouldn't want the word Nazi to be associated with me in any way.