"I love your body... it looks like a swimmer's!"
You probably mean, "Your body is toned and athletic." She definitely heard, "Nice can, Ivan Drago." Basically, there is no place for the word "like" in a compliment, so stick to adjectives, don't get too creative with the metaphors and you'll save yourself from shoulder freeze.
"Yeah, my ex really liked Metallica, too."
If you learn nothing else from the words on this page, avoid comparing her to any other woman, pretty much ever, at all costs. Whether it's that she looks like Halle Berry (bullshit), reminds you of your mom (creepy) or is as cool as your best female friend (hates her), being compared to another woman, no matter how positively, leaves too much (read: any) room for misinterpretation.
"You ate that whole thing?!"
Sure, she weighs 100 pounds and you blurted this out in a moment of genuine awe, but there is no scenario in which it'll be well received. Comments about what you're eating are annoying in general, so you should especially refrain from making them about her, including, "That's all you're going to eat?" Yep. Shut up.
"Is that all you're wearing?"
The double standard works like this: she makes fun of your Slipknot t-shirt, you tell her how hot she looks even if she's wearing a grain sack. Offering a woman any other fashion advice is asking for blood. In this case, it also makes you seem controlling. If she wants to wear a dress that's more risqué than usual, get over your boner guilt and enjoy the view.
"You're right, Heather did look hot tonight."
She won't freak out right away. But the instant you make a positive comment about the physical appearance of her friend, that thought will be double-encrypted on her hard drive forever. Feel free to tell her that her friends are cool or funny or nice—that can actually score you points. Just avoid any references to her best friend's phenomenal rack even if it is, in fact, phenomenal.