For basic camera directions in a script, you are going to describe the angles. This is done by shortening common camera directions to their base letters. Medium Shots become MS, Extreme Close Up becomes ECU and Over The Shoulder becomes OTS. From here, you put a statement about the type of angle before the description of a shot or series of dialogue. This can be in a simple statement independent of the prose passage, or included.
Example: Low Angle – President looks strait into the mirror as he fixes his tie.
Example: Low angle of the President looking strait into the mirror while fixing his tie.
This really depends on the style of the script, but it is often better to include it as a prose passage if it is in a spec script. Either way this is not going to help you sell your script