I think a lot about what I pack before any trip. "Think a lot" may be an understatement. Obsess is probably more appropriate. Part of this is because I'm a Virgo and overthinking is what we do. We are also ruthlessly efficient. (And always right!) The mere thought of packing (and lugging around) clothes and shoes, to never once wear them while I'm away, makes me physically nauseous. It's been a year and I still think of the time I went to Kenya and never wore the two tank tops and one pair of shorts I'd brought with me. I'm not sure I've ever been so annoyed with myself as I was when I realized I'd overpacked. Do I sound crazy yet? I'm being completely serious.
To me, there are few things worse than overpacking. I would rather have all my toenails ripped off than to check my bags, no matter how long the trip. I've gone months with a single large backpack or overhead bin-compliant suitcase. If forced to trace it back, I'd look straight to that time that Northwest almost kept me from spending Christmas with my family just before my brother was being shipped off to Iraq (I made it to them Christmas day) and how they also managed to lose my luggage for a solid week at the same time. The luggage that had all my Christmas presents for my family, not to mention my clothes. To make matters worse, we were also staying where my brother was stationed at boot camp so I didn't have a familiar house or any high school clothes to wear instead. But like the Buddhists, I've come to understand that the need for physical objects = suffering. We don't need so much.
Let my compulsive obsession be your gain. This is for women only, because when I think of how easy men have it, on this subject in particular, I get mad at the universe. Men don't have two different sets of pants or jeans, some that go with flats and longer ones that go with heels. Men don't have to worry about whether they need to bring heels at all! (Save for, I suppose, your occasional drag queen.) Men don't have to worry about whether their outfits match because men wear boring clothes that are basically interchangable, always. Herein lies my guide for packing:
SHOES
This is probably the hardest, which is where we're going to start. Sneakers are for those who are 100% going to be doing some sort of outdoor activity. If you're going to the beach and think, "Oh, I might run one day," don't pack them, because you won't. If you can think of at least two previous trips when you brought sneakers and didn't wear them, you're not taking them this time. Sneakers take up prime real estate in a suitcase which is why, if you must bring them, wear them to the airport.
In almost all cases, I recommend bringing no sets of heels and instead a pair of black flats that you can dress up or down. And if you must, MUST bring heels, you get one pair only, and they must be BLACK or NEUTRAL. If you're going somewhere that you'll have a few fancy parties, I'll allow you one of each. Don't even think about some multicolored pair of things that go with a single outfit only. In winter, women have it easy. A pair of black flat (or small-heeled) boots are so versatile and can be dressed up or down in a flash.
Most importantly, if you're vacationing somewhere that you'll be doing a lot of walking and sightseeing, don't bring new shoes! New shoes need to be worn in and walking the streets of Paris is neither the time nor the place. Bring those comfy ballet flats, stick a pair of insoles in them and stop worrying about whether the French women are judging your fashion choices. They're probably judging you for a myriad of other reasons first. Like because you talk too loud or aren't smoking.
CLOTHES
This part is easier if you take a few minutes to actually chart out your trip. For day, if you'll be doing a lot of walking, have a pair of jeans and a pair of leggings or shorts (depending on the weather). Bring a few tops appropriate for whatever temperatures you may face. For evening, you do not need a separate outfit for every night. If you want a dress for somewhere fancier, make sure it's jersey or some blend that won't wrinkle. Clothes that wrinkle means you're either 1.) never going to wear it or 2.) waste precious vacation time ironing your clothes. Neither of these are good options ladies! When you're packing your few separates, think about whether a certain top could go with more than one set of bottoms. If not, don't pack it. If a certain shirt needs its own separate bra, don't pack it. If you're going somewhere tropical, pack a couple swimsuits and think real hard about the rest. I say that because most people don't really wear any clothes ever on tropical vacations, much less something fancy. You'll need a couple of sun dresses or linen for dinner, but for daytime don't pack 5 pairs of shorts.
MISCELLANEOUS
You'd be surprised how much this happens to people so I'm going to remind you now: don't forget undergarments. Don't be afraid to re-wear a bra, but never re-wear underwear (hopefully you knew that already). Bring a few pairs that are seamless if you're bringing a slinky dress (panty lines are the WORST). If you're bringing sneakers or boots, don't forget socks or stockings. Always throw a lightweight sweater in your suitcase in the summer, just in case.
If I'm going away for a while, or headed to somewhere particularly hot and sweaty, I put powder detergent in a bag and bring that. It takes up no space and you have it in case you need to clean anything in a sink. Because we're not checking bags, all toiletries need to be three ounces or smaller. There are lots of containers and jars at the Container Store or your local drug store for putting things you only need a little bit of, in smaller packages. Things I keep with me always, in life, just because: a Tide pen, band-aids, ear plugs, safety pins, a stray tampon, an Emergen-C pack, and Aleve. I guarantee you will use at least two of these items on any trip. If you're a shopper, bringing a fold-up Longchamp-like tote may not be the worst idea. I've often used that as my "personal item" with my purse and a pair of shoes or two stuck inside if I ended up running out of room in my carry-on as I depart.
EXCEPTIONS
Weddings are the exception here. If you're in the wedding party you can't choose the dress or the shoes and you often need a couple of fancy outfits. You may have random day activities planned (hell, I went tubing and skeet shooting at my last wedding). Do your best to be practical. Don't be afraid to re-wear a dress. If the wedding is any fun, everyone will get so drunk along the way that they'll forget they saw you in it twice.
FINALLY
If you're done packing, have hemmed and hawed, made some sacrifices and have some room left in your bag, you have two options. First, you can pat yourself on the back and know that if you buy something you'll have room for it in your bag. Second, you can go back to your closet and grab that top and strapless bra that you really wanted to bring but didn't, because I told you it wasn't allowed. You've earned it.