Unfortunately I don't. I get them mixed up too. Heck even the other day with a Dutch tutor on skype after 45min I realized that it was harder to reach for English words.
I've heard people say that they have their own personal methods for dealing with this. One guy said he likes to think of the geography of the country and keep that in mind to keep languages apart. Another one I heard is trying to think about the culture, the gestures, the mentality. And so if you're speaking French try to be the most French in every way, which means if you suddenly say a Spanish word you will hear that it stands out. But I don't really know how to apply that advice.