"I can't say it or you'll punch me -- oh I can't hold it in! You seem to have the best breasts ever!" probably isn't going to go over all that well with the lady you are trying to e-woo. Pro tip, if you think it'll get you punched you might not want to bring it up.
Following up with "Oh but don't get mad!" isn't going to suddenly make your comment any more tactful or appropriate. No, not even if you are "just stating the obvious!"
And after your dazzling compliment, the lady in question seems less than flattered by your attentions? She will not suddenly be more tolerant or understanding or pleased when you tell her "Well it's only the truth! What, did you want me to lie?"
Just in case I need to spell it out for you, she didn't want you to mention it at all. Trust me, there is no shortage of men on the internet chomping at the bit for a chance to talk about a woman's breasts. Whatever it was you wanted to say about them, she's heard it before. Multiple times, by multiple douchebags. And usually the same thing, too. Dudes apparently aren't all that creative when it comes to boobs.
well, when it comes to talking about them, then.
Now normally I'd assume that if a guy has randomly started talking about a girl's chest, he is a raging dickwad. Seriously, it's pretty basic! Polite friendly guys do not start talking about how a girl has boobs like the Mona Lisa has paint. They do not point and make grabbing motions and honking sounds. They do not write soulful titty haikus. They do not make motorboat noises. In general, they don't make awkward, rude comments about a woman's body if they are hoping for a chance to get to know said lady.
But JUST IN CASE! I'm gonna let you in on a little secret. If you are an earnest dude trying to compliment and flatter your lady-friend, boobs are probably not the first choice you should go for. Butts and legs are also out. In general, body parts are not the first thing you should aim at when you want to fire off a compliment. You know what a good compliment sounds like? "Hey, I love your scarf!" or "You're really good at piano!" or "You do a really good impression of a penguin choking on a cell phone!" Rather than, "Your tits are boobful!" or "Yum."
boobs: probably not poisonous?
Want to know what makes them good compliments? The person you are complimenting has chosen to wear that Fourth Doctor scarf. She practiced really hard to be able to play Rach 3 flawlessly. She did a lot of hands-on research to find out how choking penguins sound, and what ring tones they would choose. Those things are indications of her choices and her personality. She didn't look at her boob closet today and go "Hmm, the C-cups will look nice today!" Her breasts are just something she happens to be shaped like. A meaningful compliment would be on something about her personality, something that is relevant to her as a person. Boobs are nice but they don't make her who she is. And when every girl gets the "i like your breasts" message all the time, it's kind of like saying "I only noticed one thing about you, and your personality is less noteworthy than the fact that you, like many women, have breasts that I would like to play with." And that just gets tiring. So please, non-dickwad guys, will you please shut up about the breasts already? I would tell the dickwads to shut up about them too, but well, they're dickwads. They wouldn't listen to me anyway, the fuckers.
Don't get mad at me,
You have nice boobs -- should I lie?
A titty haiku.