Apart from all suggestions here, one peculiar thing I have encountered in my first prelims needs to be avoided. It is "unnecessarily indulging yourself in a particular question just because you have prepared that topic well". By the time you will realise it, crucial 5/6 minutes or most will be lost. In 2018 a match the column on Wellesley came and i got too indulged in that question. Later it came out that UPSC did some word play and gave name of the brother of Wellesley (THE Wellesley). So its UPSC, other than being unpredictable, it's cunning too:D
