It depends on what site or program you're using. Usually there is an R symbol near the planet, but some sites might not mark that at all (which is a shame, in my opinion). It's definitely marked if you use astro.com. However! An important thing which many people either don't know or simply forget about is that a stationary retrograde planet may not have that mark at all, even at AstroDienst. If you want to find a stationary retrograde planet in your chart, open Additional tables PDF on AstroDienst, such planet will have SR next to it. Not to scare anyone, but it is considered a stronger debility that an average retrograde planet. Astronomically it means that the planet is changing its direction (when observing from Earth) towards retrogradation.
