Never ever tell her she looks like a celebrity: It does not matter if you compare her to Miss. Universe or Rosanne Barr, she will find something wrong with the girl or at the very least think you secretly desire this person over her. Plus it is inevitable that she'll have some catty issue with said celeb.
Then there are the various degrees of resemblance to consider. Does she look a little like her, a lot like her or is it just in “this light?” Very dangerous turf to tread and it will always cause you gastritis.
Example
You: “Honey did I ever tell you, you look a little like Demi Moore?”
Her: “What? How much? You mean Ghost or St. Elmos Fire? Did you notice she has a huge fat neck? Is that what I look like? A huge fat necked cry baby who divorces her husband and hooks up with a boy half her age? Nice. Real nice.”
If you must make a comment about her appearance, tell her she doesn't look a second older than the day she stole your heart.
They eat that crap up.
If she comes to you with a “great idea” and it doesn't include football, beer, cheeseburgers or modeling lingerie - go with it: Whatever you do don't resist. Females see this as a sign of defiance and will greet it with great vengeance. You WILL end up sleeping in your car or worse - at your parents' house.
Example
Her: “You know what I was thinking we would do today? Take a drive out to the country and have a picnic with a little sushi, nice baked brie and a spinach quiche. What do you think?”
What you'd better say: “That sounds delightful, my love. Maybe after we could go shopping, or to a spa, you know - completely get away from the tee-vee.”
What you'd better not say: “But then I won't be watching television. Nah, I think we should just get some wings, a twelve pack and check out the game.”
When (not if) you go shopping with her, make sure you are feminine enough to support her and masculine enough to make her feel confident: (Assuming you answered the example in #2 correctly) If she shows you different outfits or shoes or earrings or what have you and wants to know which you think she should buy, open the estrogen valve and let its soothing flow guide you.
Say something like, “gee sweetie, I really don't know. I love the cut of that dress and the pink shoes are so cute… but the green on the other dress really brings out your eyes and the black shoes give you a sharpness I didn't feel from the other outfit. Tell ya what - I'm thinking we should just get them both… you know, so you can choose whenever you want and not just this once.” This is tricky but with lots of practice you should be able to sound sincere.
Warning: Never choose one over another: It will spark a feeling that you just want to get the hell out of there and care about which item she buys as much as you care about Oprah's book of the month club. Although true, this will have the opposite effect and dramatically increase the time you have to endure the department store. She'll slow her pace and go from rack to rack purposely detaining you and screwing up your chance to see the afternoon reruns of Walker - Texas Ranger.
Furthermore, she will immediately detect your futile attempt at escape and suppress her reaction until she needs the ammo - long after your brain wrote the memory off as “no biggie” and purged it.
If she asks you what you want for dinner, always name one of her favorite dishes - then offer to cook it or take her to the restaurant that makes it best: The latter is the preferred response because at least then you can get whatever you want to eat, but you must mention the first option or she'll think you don't want to “put any effort into this relationship.”
Never, ever say, “I don't know, what do you want?” Because when she asks questions of this nature she is giving you the opportunity to do “the right thing.” By putting the decision back in her lap you have failed the test and will never recover. Trust me - it could be 10 years from the incident but she will bring it up in a fight, which leads me to number 5...
During an argument, make absolutely certain you have your facts straight, are sincere with every word and do not mock her: First, if you don't have your facts straight, you are done before you start. Women will always be right, always have all the facts - yes, they are that observant - and have memories that go far beyond the understanding of mere mortal men.