Well if you want to know more about Singapore first visit the Singapore official tourism website. It will give you info about all the best places in SG. List down the places names that you would like to visit and try to do some research for reviews on those places. If people have given good reviews then it would be worth visiting.

According to me the best places are National Orchid Garden,Botanic Garden, Zoo, Marina Bay, Budhha tooth relica temple and museum, Sungei Buloh Wetland Reserve and many more. Best thing is try to find it out yourself and happy travelling :)