If $r$ or $\theta$ are equal to a number, then it's easy to graph by hand.
If $r$ is a number, then $\theta$ will take on all possible angles!
Conversely, if $\theta$ is a number, then $r$ can take on all possible distances!
Polar equations can be written in the form $r = f(\theta)$.
In English, this is "$r$ is a function of $\theta$," meaning, plug in an angle $\theta$ to determine how far you need to walk in that direction $r$.
A few examples are \[r = \theta \qquad \qquad r = 2\cos \theta \qquad \qquad r = 1 - \cos \theta\]
Here's an animation of the previous problem. Notice how the length $r$ is like an "arm" tracing out the graph:
Most polar graphs in the form $r = f(\theta)$ are difficult to graph by hand. Use Desmos to help you.