The easiest way would be to set a deadline on each task (Task Information window -> Advanced tab). This shows a deadline icon at the appropriate place in the Gantt against each task thus set.
In addition you can set a constraint of "Finish no later than" on the Task Information window -> General Tab
If you want to be very obvious and show an explicit milestone for the deadline then set a milestone task with a "Must Start on [the deadline date]" (auto-scheduled tasks only) and make each relevant task a predecessor of the deadline milestone- that way if any task overruns it will try to push the milestone to the right and you will get a scheduling error.
Any of these can be used singly or together depending on what you need to accomplish.