Have taken CAT last year ...Here's my input..
# Be seated in your allocated seat as early as possible.....You'll get loads of time to fill the OMR sheet and cross check it .. The invigilators are supposed to complete the formalities in this time and not after giving you the Qn paper...
If you turn up late then u're bound to get disturbed by the invigilators' formalities and u'll be tensed while filing the OMR in a hurry ...
SO be before time and finish the formalities....you'll get ample time to gather your thoughts and cool your nerves ...
Other factors such as noise , functions , processions which are not in control of the examination center cant be avoided ...so it wud be better if u're prepared mentally for any such kind of stuff...
Keep your cool and nothing else wud matter ....

..( Tried this by taking a mock when everyone was trying their best to make noise with the firecrackers ...didnt affect my performance by a bit ...

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