I went to a bilingual emersion elementary school, and I switch between English and Spanish a ton when I'm thinking. Especially during school, I'll have Spanish earlier in the day, and then have to make it through English class while ocassionally thinking in Spanish. I'll also take notes in Spanish to help stay focused, since I can study from it either way, just have to translate as I take them. I think it is an advantage, because you aren't limited by vocabulary in one language or another, and you can adapt to use the language, mix of languages that's fastest and easiest for you.
Mostly actively translating. It is pretty much the same trick as repeating stuff in your head to help pay attention, but I find it a bit more mentally challenging as concepts often do not translate very well. However, at other times, Spanish words will slip into my English notes without me noticing.