Common Sense Note
Parents need to know that some critics have interpreted an unsubtle anti-religious message here. The villain is a religious fanatic with a barbaric flock of pilgrims and a fondness for mind control. As for the vague, godlike being (perhaps even the God) he seeks, it comes across as a manipulative, power-crazed alien-monster menace. There is also drinking, mild curse words, and some fist-fighting and ray-gun violence. A brief subplot involves physician-assisted euthanasia (portraying it more or less with disfavor).
Uhura does a skimpily clad dance to distract some bad guys. There is a catlike alien woman with prominent (multi-breasted) cleavage.
Ray-gun and rifle-type fire, bloodless hand-to-hand combat.
"God-damned" and "pisses me off" uttered.
Starfleet is notably racially and species-integrated, and there is a strong sense of friendship, military duty, and loyalty (Mr. Scott won't disregard an order to get a transporter working, even with Klingons and God on the attack as potential distractions). Religious believers, though -- to the extent that the cultists here can be described as such -- are pretty much brainwashed, uncivilized rabble.
Drugs / Tobacco /
Dr. McCoy praises the merits of Kentucky bourbon. Drinking in a riotous interspecies bar. Klingons are shown especially drunk.