a photocopy of a document should be carried at all times, as it is mandatory by law, and very useful in case of emergencies.

expensive smart-phones should be left at home, and only basic cellular phones should be taken out - best if local, so that coordination with friends would be easier via sms and texting. 

bringing a bottle of water is always a great idea, since dancing and singing in hot whether can be exhausting, especially for visitors who are not used to this type of celebration.

a hat and sunscreen should also be used, as the heat and the strong sun are not only at the beach, but everywhere in rio - exhaustion and dehydration are common problems para unprepared partiers.