There are certain words and topics that may shut your set down if you aren't feeling out the waters carefully first: skulls, death, destruction, sickness, illness, plague, 9/11, disaster, violence, conspiracy, religion, politics, guns, crime, rape, torture, molestation, abortion.
You can discuss these issues or use these words, but do so with caution, because they could easily lead to a dark, depressing convo. In general, there is never a good reason to compliment a girl about her beauty or any of her physical features. The same applies to tattoos. You might say ?Oh, this is a cool tattoo? but since guys have probably used that one a million times, you should neg with something like ?is that supposed to be a map of Utah?? Likewise, if a girl has some physical imperfection, DO NOT bring it to her attention, and stop your eyes from wandering to it. You must at all times show indifference to her physical appearance, and always instead emphasize other positive features like her laugh, her humor, her ability to walk in high heels, etc.