You can always tell the difference between a star and a planet.

Stars have a Pulsar, which means when you look at them they appear to flash, if you look at the stars in the sky they twinkle, thats the pulsar

Planets don't have this so they just appear to be a star without a twinkle, although mars can appear to change red/green sometimes this this is the shadow of the earth. Other planets you can see Venus nearly everynight at dusk