That's pretty much it. Second, don't panic. Third, go with what you know. Four, start your assignment. If you do, you're dead.
Panic kills the capacity to react.
Thus, when you're handed a project that seems impossible, spend a few minutes to sketch out, on paper, what you think the problem is. If you're still lost, and your Senior doesn't shed some light, sua sponte, make a motion to that effect. Go back to your Senior for clarification, or to another Knowledgeable One if the question is innocuous enough and your embarrassment quota has been exceeded. Save yourself endless hours in searching for complex answers to simple questions. They'll likely have an immediate answer or give you time-saving leads.