In this paper we have presented several theoretical results and an algorithm for properly plotting curves parametrized by rational functions in polar form. Our results allow to algorithmically identify phenomena which are typical of these curves, like the existence of infinitely many self-intersections, spiral branches, limit points or limit circles. Furthermore, the algorithm has been implemented in Maple 15, with good results. Natural extensions of the study here are space curves which are rational in spherical or cylindrical coordinates, curves which are algebraic, although non-necessarily rational, in polar coordinates (i.e. fulfilling h(r,θ)=0, with h algebraic), and similar phenomena for the case of surfaces. It would be also interesting to analyze the curves defined by (implicit) expressions of the type f (r,sin(θ),cos(θ)) = 0, where f is algebraic, since this class contains, and in fact extends, the class of algebraic curves; also, it includes the important subclass of curves defined by equations rn = g(θ), with g(θ) a rational function, which often appear in Geometry and Physics. Some of these questions will be explored in the future.