The most important thing to remember when drawing ray diagrams is that the angle of incidence (
Draw a normal, that is perpendicular to the reflective surface at the point where it touches the surface (the point of incidence.)
Draw the ray of light that is striking the reflective surface at the point of incidence.
Measure the angle between this ray (the incident ray) and the normal. This angle is the angle of incidence.
Measure an angle on the other side of the normal that has the same measurement as the angle of incidence. This will be the angle of reflection. (
#theta_i = theta_r#)
Draw the reflected ray in its proper place.
For more information, check out http://www.physicsclassroom.com/class/refln