how to reserve a seat in Singapore

Use a packet of tissue! 

This method can be used at the hawker centres and food courts in malls. Food vendors in both don't give tissue when you buy meals from them so people here always have a packet of facial tissue at hand. It doubles as a way to reserve seats, especially during lunchtime when hawker centres and food courts get packed. The practice is so ingrained in the culture that merchants use tissue packets to market their products and services, like the one in the above photo.