1) When buying certain edibles, don't skimp. Don't be tempted by generic brands that look the same or by no-name prices. Your taste buds and stomach will thank you. My list includes pickles, mayonnaise, ketchup, ice cream, maple syrup, Coke and champagne. It's better to spend a little bit extra and actually see the bottom of the mayonnaise bottle after a few months instead of throwing out an almost-full jar. It also prevents long lectures from disgruntled husbands ("You didn't buy HEINZ ketchup? Kimmy, there ain't no other kindz!"). Plus, life is too short to drink crappy champagne or fake Coke.
2) Buy good sheets, no lower than 300 threadcount, preferably Egyptian or organic cotton. Trust me on this one: once you have experienced the soft, gentle embrace of good sheets, you will never again suffer your body to sleep on scratchy polyester disasters from Zellers. Even D, who was a die-hard flannel sheet aficionado, has become a convert to my silk/cotton blends.
3) Some dogs just want to chase cats. No matter how much time you spend trying to teach them that cats are not their personal wind-up toys, or encourage a feline/canine dialogue, certain dogs are hard-wired to chase small furry things. No amount of patient instruction or angry yelling will help. It's easier to accept this phenomenon and strategically prevent said dogs from having kitty contact.
4) Men think farting is funny. This does not change with age, maturity or marital status. No amount of dirty looks or talks about respect or how when you were dating they never passed gas in front of you will ever change this. *sigh*
5) Some people are just better than you are at doing stuff. Writing, baking, scrabble, witticisms, decorating - there's always someone who can do it better than you can. And that's okay. Cause it probably means you can do something better than someone else out there too!