The common mistakes that I noticed candidates making before/during prelims, some of which even I made and hoped that I hadn’t are as follows:
Not sleeping well before the exam! Not a good idea at all, especially because you need to give two exams, one in the morning and another in the afternoon so you need enough stamina/mental alertness/concentration etc to last the whole day. Sleep for at least 8 hours on the day before the exam.
Completely neglecting CSAT because it is qualifying. This is THE most common mistake I have seen people make. I agree you need only 66.66 marks to clear CSAT but over confidence or completely ignoring this paper might land you in a very sorry position where you get exceptional marks in Paper 1 while you don’t even qualify Paper 2.
Not utilising the 3 hour break between the two papers appropriately.Generally after the first paper a candidate feels that the pre exam is over as all depends on the first paper. This is far from the truth. You still need basic qualifying marks in the next paper. So DO NOT spend the break in random chit chatting/ gossiping or engaging in paper discussion! Use it to relax and calm your brain for the next exam.
Attempting way too many questions without knowing the answers. Flukes generally do not work in the UPSC CSE prelims examination. If you are unsure of an answer don’t just blindly attempt thinking more questions = more marks. In the first round attempt those which your are absolutely sure of, you should be done with this in the first one hour 15 mins. After that go back to only those questions where you are down to 2 options, here you can still make an intelligent guess. Note the keyword being INTELLIGENT.
Having a pre determined cut off in mind and trying to ensure that you attempt enough to achieve just that much marks in the first paper. I met quite a few people who attempted less questions or more questions purely based on an imaginary cut off in their head. They thought getting marks equal to that will ensure their selection but instead last year’s cut off turned out to be more than they imagined! So please just attempt whatever you know and leave what you don’t. Don’t try to achieve a random cut off.
Completely skipping current affairs for pre. Many people expect pre to be purely based on NCERTs and other basic books, while this was the trend a few years ago it certainly isn’t now. Current developments is very important and bulk questions are asked from it in the prelims exam as well.
Focussing too much on just the core subjects like Polity, Economics for prelims while neglecting the others. It is being observed over the last few years that relatively questions on Environment, Art and Culture and Current Affairs are asked more in the exam. I have met quite a few candidates who completely ignore these thinking that they can scrape through prelims by just the basic subjects. This plan backfires.
Not carrying an ID proof along with admit card. Some centres ask the students to furnish a photo ID proof along with their admit card to cross check their identity. In my centre the same thing happened and we saw many students were not carrying ID proofs. These students were allowed to appear in the exam but they lost valuable time from their 2 hours of the paper 1.
These are a few mistakes I could recall now, if I remember more I’ll add those here.