You cannot "mitdenken" in absence of a group or task that requires your present attention. Also, to proceed in a considered fashion, not thoughtlessly. Used in the imperative, it urges the listener not to be a passive participant, (as in "don't mentally check out"). It is usually rendered in English as "think ahead" or "follow along" – both miss the mark considerably. German already has a word for the former ("vorausdenken" which applies strictly to the future, not the present), and the latter does not really place the listener at the forefront of the group or task at hand. [Definition on duden.de](http://www.duden.de/rechtschreibung/mitdenken) EDIT: one word.