Queues are used for everything here, and you absolutely should follow the queue, as cutting in line is extremely rude. Before you queue up for your food at a hawker center, however, you may want to find a seat for yourself. Another interesting custom is that while you may see an empty table and sit to claim your seat, in reality, the seat may have already been taken. Singaporeans often reserve, or chope, their seats by placing a packet of tissue on the tabletop. If you see a packet of tissue on the table, then it has already been reserved and you will have to keep looking!
While there are many customs and traditions here, a fourth and final tradition is one of keeping to the left. While on an escalator, or even walking on the street, the general unspoken rule is to keep to the left if you are slow. The right side on an escalator, for example, is to be used by those walking up the escalator instead of standing and waiting for it to take you up to the top of the stairs.
Many of these traditions are unspoken rules to keep society more orderly. I like to think of them as laws that can't be laws because they would be too strict for people to be punished over if they did not follow them. While it may be rude not to call an elderly man "uncle," it is not a criminal activity not to do so. This made it so this practice became an unspoken law through tradition and is considered customary in Singapore. Many of these customs and traditions have developed out of ideas of respectfulness and the thought that they are more logical. For example, having the slower people line up on the left makes sense so that anyone who needs to move quickly can pass them on the right.
