It is generally believed that unless you know someone in the lift, or have been conversing while waiting, it is best to not engage in conversation while the car is in motion. Loud singing, whistling and other noises are strongly frowned upon.
Most people will keep their eyes fixed to the overhead number display rather than looking around at other passengers. However, unless there is an indication of discomfort, looking around at the others is permissible as long as you do not invade their privacy(such as looking into purses for example).
A rule that would most apply at this point, although should be attended to earlier is to reduce or preferably eliminate body odour. This applies to strong perfume as much as it does to not having showered for a week. The interior of a lift is a small space and odours travel to each individual aboard. What one considers to be a pleasant aroma is highly subjective. Similiarly, food and alcoholic drinks should not be consumed in a lift. Soft drinks are generally acceptable