I was speaking to an experienced lecturer recently who told me he could usually tell which programming language a student had learnt to program in by looking at their coding style (more specifically, when programming in other languages to the one which they were most comfortable with). He said that there have been multiple times when he's witnessed students attempted to write C# in Prolog.

So I began to wonder, what specific traits do people gain from their first (or favourite) language which are carried over into their overall programming style, and more interestingly what good or bad habits do you think people would benefit from or should be wary of when learning specific language?