its all aboutthe 2 hrs.however good is your preparation. (considering the UPSC pattern lately)
exam hall tactics-
-- keeping calm
--minimizingsilly mistakes(most imp; can't make easy Q wrong)
--maximizing the available knowledge base
before exam-
all subjects- good preparation (can't avoid any major subject )
any onetest series-for confidence building and developing Q solving abilities aka Tricks.
(fresh Test series isindispensableeven if you have cleared pre in your last attempt)