As a person with lots of flight experience, I can give you loads of tips. I've never traveled outside the US, but if you're flying within the US I can give you lots of pointers.
First off, as one other person said, check your airline's website for their policies.
The one thing I can not stress enough is to be there at least an hour and a half before the time your flight is scheduled to leave. Some airports even want you there 2 hours before. Check your airport's website, they will tell you. And trust me, BE THERE that early. Your time in line waiting to check in will be less, and trust me, by the time you get checked in, get through the security checkpoints, and find your gate, you will be glad. You may spend quite a bit of time waiting at your gate, but it's better than having to hurry. Bring a book or Ipod.
Secondly, if you bring ANY kind of electronics - laptop, camera, ETC. DO NOT CHECK IT. Put it in your carry on. Airlines beat the honeysuckle out of your luggage, so don't put anything in your checked luggage that you don't want broken. The baggage handlers (ramp rats in airport terminology) are on a time limit, as well as constantly being told by their bosses to "hurry up and get it loaded", so your luggage will be thrown around from the time it leaves the hands of the person you gave it to that checked you in till the time it gets to the conveyor belt at your destination. And there are the stories of theft by airline/airport employees too. If you have anything that gets lost or damaged, trust me, the airline WILL NOT work very well with you to make it right, so keep your valuables in your possession.
next, many airlines no longer provide complimentary food or drink in flight. Some will, but others won't so much as give you a glass of soda without charging you for it. So if you think you will get hungry in flight, bring food or drink with you.......which I should also mention, food or drink from the outside is not allowed through the security checkpoint. if you bring it they will make you throw it out. So, if you want to take food or drink on the plane with you, it HAS to be bought at one of the airport stores that are past the security checkpoint.
You may want to think about packing a set of clothes in your carry on, in the event the airline mis-directs your checked bag. It's rare, but it happens. Again, ramp rats are under a lot of pressure to hurry, so baggage gets misplaced on the wrong planes at times so it goes to the wrong destination, and it will take you a day or 2 to get it back should this occur.
As for carry ons: You are allowed to bring one carry on bag and one personal item. I pack all my electronics, CD's, ETC in my carry on bag. My laptop is my personal item. (If you travel with a laptop, they will make you take it out of the bag and X-ray it separately.) This policy holds true with ANY airline, as it is a federal regulation.
Most airlines charge you to check bags, so find out how much it will cost for each bag you check. Some allow the first bag free and charge for each additional bag, others charge for every bag. Southwest does not charge to check up to 3 or 4 bags I think. Delta will let you check your first bag free, and charge for each extra bag. US Airways charges for every bag. Keep this in mind when you are packing and try to have as little luggage as possible.
If you decide to carry on your shaving kit or anything like that, there is a whole set of rules regarding any kind of fluids. It is very important you know the 3-1-1 rule, which is explained on the TSA website. Check it out here.
http://www.tsa.gov/311/index.shtm
you can put as much fluid (like shaving cream, toothpaste, ETC) as you want in your checked baggage but if you carry it on, you are only allowed 3 containers per passenger of toothpaste, hairspray, ETC. Each container can not be more than 3.4 ounces. you are only allowed 3 containers, and you must put them in a clear ziploc bag that is no larger than a quart size bag. Security will make you take your ziploc bag out and put it separately on the X-ray scanner so what I usually do is if I bring it in my carry on, I have it in my front zipper compartment of my carry on bag so all i have to do is pull it out when they tell me to. The travel size containers of stuff like that you can buy at wal-mart are usually less than 3.4 ounces, so they are perfect. Razors in your carry on bag are a big no no, although i think if they are in a cartridge, they may allow them.
The size of your actual carry on bag is limited too. TSA's website will give you the dimensions of how big it can be.
A word of advice when you get to the metal detector....take EVERYTHING out of your pockets. they give you a bowl to put your keys, cell phone, wallet, ETC. in. While you are walking through the metal detector, they will run this bowl through the X-ray with all your other stuff. those metal detectors will pick up a single penny......so be sure to make sure nothing is left in your pockets or they will keep making you walk through until you don't set it off anymore.
Once you are on the plane, just listen to the announcements. they go through everything you will need to know about the flight.
If you have to change planes, trust me when I say this: Find out what gate your next flight is at, and get there immediately. Even if you have a long layover. some airports make you take a bus to your next gate, or if it is within walking distance, many times you won't have much time to find the gate before your next flight leaves.
If you are hungry, have to go to the bathroom, whatever....find your gate first. once you find it, THEN go eat or do your business if you have time, otherwise you may miss your flight.
Also a word of advice....usually when your plane lands, they tell you what gate number to go to for the plane that is going to your next city. Listen for the gate number, but even at this, be sure to double check the monitors inside the airport. they will tell you what gate your flight leaves from. it never hurts to double check, in case they decide for whatever reason to switch your gate. Once you get to your gate, there is usually a sign at the gate with your flight number and city. if you see that sign, you know you found your gate.
Once you land at your final city, they will tell you what conveyor belt to pick your bags up at. Just follow the signs and you'll be good to go.
It's not bad, but if it's your first time, you may have a lot of trouble if you don't know the ins and outs. I'm an airplane buff and I love flying but the airport stuff can sometimes be a hassle, especially your first few times.
Have fun, and good luck. I hope you have a great time. let us know how it goes.