Why don't any Cishet men know how to compliment a woman?
You want to make them feel desirable, but not Desired.
You want to compliment their Choices, not their Body*
You want to be Kind, Positive, and Observant. This isn't about You, it's about Them, and making them feel more secure and confident in their appearance and to a degree, Body.
And brevity is the soul of Wit. Make it concise, pleasant, and don't overstay your welcome.
*Trans Girls slight exception.
Tell them their boobs are big