To observe the transit of Venus directly you must protect your eyes at all times with proper solar filters.
Observing
The safest way to observe a transit is to project the image of the Sun through a telescope, binoculars, or pinhole onto a screen, but the event can be viewed with the naked eye using filters specifically designed for this purpose, such as an astronomical solar filter with a vacuum-deposited layer of chromium, eclipse viewing glasses, or Grade 14 welder's glass. An earlier method of using exposed black-and-white film as a filter is no longer regarded as safe, as small imperfections or gaps in the film may permit damaging UV rays to pass through. Also, processed color film (unlike black-and-white film) does not contain silver, and is transparent to infra-red. This may result in burns to the retina. Observing the Sun directly without filters can cause a temporary or permanent loss of visual function, as it can damage or destroy retinal cells.
Points of Transit
There are four named "contacts" during a transit — moments when the circumference of Venus touches the circumference of the Sun at a single point:
First contact (external ingress): Venus is entirely outside the disk of the Sun, moving inward
Second contact (internal ingress): Venus is entirely inside the disk of the Sun, moving further inward
Third contact (internal egress): Venus is entirely inside the disk of the Sun, moving outward
Fourth contact (external egress): Venus is entirely outside the disk of the Sun, moving outward.
A fifth named point is that of greatest transit, when Venus is at the middle of its path across the solar disk and which marks the halfway point in the timing of the transit.