Monolingual or Bilingual dictionaries?
I prefer bilingual dictionaries for lower levels. This gives them a quick answer to their questions, without raising a whole load of new ones.
For higher levels, monolingual dictionaries are better, and students at this level are more tolerant of them, I think, and less likely to feel demotivated if they don't fully understand something.
I have to say that I don’t use dictionaries a lot in my classes. We don’t have many of them in the school. With my CAE class recently, I recommended that they downloaded the word reference App, as I find this very useful myself. I quickly looked up the word for 'holly' the other day, for example, & we all learnt something!
I very often rely on my own knowledge of Spanish/Catalan to provide students with a translation in class. Nearly all my classes are monolingual, which makes this possible.