As a seasoned traveler I wanted to share some tips with you. I never over pack because I type up a spreadsheet of what I will wear everyday. This way I only take what I need plus an extra dress for an improtu evening and one backup if something goes wrong with a scheduled outfit.  At home I try on every outfit to see which jewelry goes with it and also jot that down on the spreadsheet under the jewelry column. While on vacation, when I go to bed every night I refer to my list and hang up the next outfit in the closet so it's easy and ready to go in the morning. So no matter how I feel when I wake up (tired, etc), I always look good. I always bring a sweater and socks because airplanes are always cold.

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1. First start with a packing list because it's always the little things that you tend to forget that are a pain to find overseas. You can also download an app called Packing Pro that can help you with that and what's great about it is you can customize it and have separate lists for your carry on and each traveler with you. Plus you can save your list for future trips!
2. There's two theories on how to pack some people say rolling your clothes takes up less space and the benefit is rolled clothes are less prone to wrinkles. I however prefer to use space saver bags so all my clothes are in plastic bags, but some items do end up being wrinkled on their folding crease. I tend to stick to dresses that don't wrinkle so for the most part I'm ok. I figure if TSA goes through my bag everything stays in order because it's easy for them to just lift up the bags. I also have one bag just for large bottles.
3. Weigh your bag before you go, for international flights the limit is 50 lbs. If you are a big shopper than your bag should weigh considerably less than that so you have space to add to it.
4. Buy travel sized liquids. I saw at Bed Bath and Beyond had great empty kits that come with a pouch with bottles you can fill yourself with your favorite products.
5. Never check essential items. I keep all my makeup in my carry-on. I know that may not essential to you lol, but as I don't take any medications that's about the most important thing I carry that would be a pain to replace.  I also keep a spare outfit and swimsuit in my carry-on in case my suitcase gets lost and doesn't make it to my destination.
6. Keep your money in a money belt. I'm not a fan of wasting time running around to find ATMs and being charged outrageous fees. A friend of mine was charged a $30 foreign transaction fee every time she took money out in Spain!
7. Use packing aids to organize your suitcase. I use these Smart packs to pack my lingerie, makes them easy to find in one place. I'm a huge fan of separating things by category into their own pouch. 
8. A travel pillow is a must have!
9. I see lots of women throwing their gym shoes into their purse, I prefer a separation of cleanliness because after all the bottom of your shoes aren't clean. In my suitcase I use a shoe bag.
10. Bring a battery operated alarm clock, because I've seen cases where the hotel forgets to give you your wakeup call and your iphone isn't charged. If you're going international you'll need travel adapter plugs.
11. Bring facial wipes because at the end of a long tiring day, you'll be too tired to go through your makeup removing routine. Not only do these wipes remove makeup, they take off your mascara!
12. Have a unique looking suitcase so it's easy to find yours! At the luggage claim I could easily sit far back and relax as the luggage came out because I can spot my pink bag a mile away! I have a kitschy yellow luggage tag that says "This is not your suitcase". You don't want to opt for the paper tags at the airline check-in while hastily scribbling your addresses and phone numbers because that could easily fall off. I saw on the news that there are many unclaimed suitcases every year. I also print out my address in large font on a piece of paper and put it inside my suitcase.
13. All the hotels in Spain had free wi-fi in the lobby and sometimes also in the rooms, although they charged you to use their computer if you didn't bring your own device. Many restaurants, fast food chains, malls and rest stops/gas stations also had free wifi. I saw a number of people with either the mini ipad or kindle fire and realized, that really was the perfect travel sized device. The people who only took photos on their phones frequently ran out of space and had to move their photos over to their ipad.