Position of the Planets
Before asking yourself where the planets are in the sky tonight, why don't you look at the Solar system as a whole to see the relative positions of the planets with respect to Earth?
A dynamic model of the Solar system is called an Orrery. At the present day it is easiest to display the model as a Flash movie on a webpage, such as the excellent one below created by INOVE.
Where can we see the planets tonight?
Imagine yourself on planet Earth and look at where the planets are with respect to the Sun. Any planet behind the Sun will of course be invisible. Planets in opposite direction as the Sun will typically be high in the sky at midnight. A Planet to the East or West from the Sun as seen from Earth will be either in the morning or in the evening sky. Realising that the Earth rotates toward the East, where do you think these planets are, in the morning or evening sky?
(You can check your answer with the monthly Night Sky report here)