The amount of times this happens is just ridiculous...
1. Always leave extra room in your suitcase! First off stuff will never fit back in the way it did when you got there, don't ask me why but it never does. Second, you will always end up bringing back some extra stuff with you, especially on long trips. If your suitcase it stuffed to the brim when you leave, your doomed.
2. Stuff your shoes with socks and/or anything you don't mind getting a little bunched up and wrinkled. That was all that inside space of the shoes isn't left empty and wasted.
3. Double bag any kind of liquid. There will always be that one bag with a hole in it no matter how well you check them, and hand cream is not an easy thing to get out of clothes.
4. Lay things out flat instead of rolling or bunching the up. It takes up a lot less room and stuff won't get as wrinkled!
5. Put any breakables/liquid items in the middle of your suitcase (double bagged of course) so that they are protected by the clothes around them.
6. If you need a change of clothes at the airport and can't fit them in your carry on, put them at the top. That way at the airport you don't have to lay out your suitcase and dig through it to find what your looking for, you just unzip the top and it's sitting right there.
7. Lay belts around the outside of the suitcase instead of rolling them up. Just learned this one from mom and it takes up so much less room!
8. Pack things in order of what you think you will need from top of the piles to the bottom. That way if there's no where to unpack where you're going you won't have to go rummaging through your suitcase every morning.
9. Pack versatile things. A basic white t-shirt can be worn around a flight line with short and sneakers, jeans and a purse for casual dinner, or put with a skirt, jewelry and heels for a night out. Bring shirts that can be worn with any of the bottoms you have/bring bottoms that can go with everything. You never know what you're going to want to wear and if you pack a bunch of specific outfits you will never end up having the combination that you're looking for.
10. Even if you're going somewhere hot (south western Texas for example), bring a sweater. You will most likely end up wanting it on the plane to cozy up in if you don't have a blanket, but if you plan on going out to dinner or a movie the air conditioning will almost always be turned on way to high to compensate for the heat outside and you're going to freeze. Just make sure that it's something that can dressed up or dress down.
11. Ladies; don't pack all of the makeup/hair products/shower stuff that you own. It takes up more room than you would think and you will never use it all. Bring the basics! Things that can serve multiple purposes are ideal, such as shower gels to double as shaving cream and combination palettes of makeup. Chances are wherever you're going you will be spending way more time enjoying yourself than sitting in your room getting ready.
12. Don't buy massive suitcases unless you're okay with paying more to fly with them. Yes I have a suitcase that I can fit into and yes it's awesome for holding tons of stuff but if I fill it up completely it is always over the weight limit. As in $150 for those few extra things that you really didn't need. Not worth it!
13. Always bring running shoes and workout clothes. You never know where you'll end up going and chances are at some point you will need them. Wether it's for a workout at a hotel on a road trip, an impromptu hike somewhere or just going for a run to watch the sun rise they will always come in handy.
14. Leave a pocket in your carry on to put your passport/ticket/ID all together. Leave this pocket for only those things and always put them back there. Then you avoid being that crazy person tearing apart their bag at the counter trying to find it all!
15. Pack cash. Visa cards are great but they can be a pain depending where you're going. For example small cafes and restaurants often have minimum purchase limits and american gas pumps won't accept Canadian visa's. If you have some cash you can at least survive and pay for things until you figure out what the easiest way to pay is wherever you are. That being said don't carry a lot of cash in one single place. If all of your money and cards are in one purse and it gets stolen things don't look to good.
16. If you're going somewhere that speak a different language, make a translation book your airplane reading. Being able to show up to another country with a few basic sentences in their language will not only make your life easier, but people will also be a lot more welcoming when they see you putting the effort it. If only Australia had a language book for all of their slang!
Now you're packing like a pro!
So as of now, that's all the helpful things I can think of. I'm sure the more I travel the more things I'll have to add to this list! Headed to Tasmania for a week at the end of the month and we didn't want to pay to check baggage so we've got to pack in a backpack carry on. Challenge accepted :D