I wish to comment on your comment about negative marking. If you are sure you will not be guessing on more than 50% of the questions, guessing may be your friend whether negative marking is in place or not. Note that the purpose of negative marking is to make sure you don't get undue advantage as a result of any special talent for guessing (pun intended, but I hope you understand), and not to punish you for guessing. With negative marking, your wrong and right guesses are assumed to even out (really nice, ehn?)
Besides, if you are not told specifically there is penalty for guessing then there is no guessing penalty. I can assure you of this!