There are no special taboos, but remember to be polite and speak quietly. You can't speak loudly like you do at home, which will arouse the contempt of the other party. For example, when asking for directions, you must say "I'm sorry" before "thank you", otherwise the other party will think you are uneducated and look down on you. Many China people feel discriminated against in Singapore, and many of them are looked down upon for lack of education.