During the six hour long spectacular transit you can see the shadow of Venus cross Sun. The transit of Venus occurs in pairs eight years apart, with the previous one taking place in 2004. The next pair of transits occurs after 105.5 & 121.5 years later.
The best place to watch the event would be a planetarium nearby with telescope facility. If not you watch it directly but must protect your eyes at all times with proper solar filters.
Where can we see the transit?
The transit of Venus is going to be clearly visible in Europe, Asia, United States and some part of Australia. Americans will be able to see transit in the evening of Tuesday, June 5, 2012. Eurasians and Africans can see the transit in the morning of June 6, 2012.
At what time the event occurs?
The principal events occurring during a transit are conveniently characterized by contacts, analogous to the contacts of an annular solar eclipse. The transit begins with contact I, the instant the planet’s disk is externally tangent to the Sun. Shortly after contact I, the planet can be seen as a small notch along the solar limb. The entire disk of the planet is first seen at contact II when the planet is internally tangent to the Sun. Over the course of several hours, the silhouetted planet slowly traverses the solar disk. At contact III, the planet reaches the opposite limb and once again is internally tangent to the Sun. Finally, the transit ends at contact IV when the planet’s limb is externally tangent to the Sun.
Event Universal Time Contact I 22:09:38 Contact II 22:27:34 Greatest 01:29:36 Contact III 04:31:39 Contact IV 04:49:35
Transit of Venus animation
Here is a nice video animation on the transit of Venus
Map courtesy of Steven van Roode, source NASA