In general, they determine your age according to your exact date of birth and not the year that you are born. Legally, you are still under 18 and will not be permitted to enter the club premises.

Apart from the legal age limit of 18, all other minimum age requirements (e.g. 23, 25 etc) are determined by the clubs themselves. This is to attract certain class of clientele and not due to the law.

Yes, it is true that slippers/sandals are not allowed in certain clubs.

List of clubbing clothes, accessories and trendy fashion sites

List of drinks to order

Generally a driver licence with your recent photo should get you through. BUT some club bouncers are pretty uptight about I.Ds. So for a great clubbing experience, club with your passport.