Preparing astronomical observations and observing with OHP facilities

In addition to the general introduction to observational astronomy given in a past paper (J. Phys. IV France, ERCA 07 (2006) pp 373-390) some tools are given to the observer. These include the general knowledge of what is going to be observed and of the instruments used. A guideline is given to prepare an observing program and to follow it as efficiently as possible. Finally, some examples are given of observations to be made by ERCA participants at OHP observatory.