Top 5 things to pack in your carry on:
Headphones: Some airlines give you a pair for free but if you ask me, they're uncomfortable or recycled from the person before you. I've sat next to enough gross people to wonder what the person in my seat on the prior flight looked like and hope he didn't use those headphones. I vote to pack your own
Magazine/Book: Don't rely on the airline to provide an interesting magazine in the seatback pocket. While the SkyMall catalog will keep you busy for a little, it won't last you an entire flight. Pack according to your interests and a little gossip mag won't hurt. As much as many of us won't admit it, myself included, gossip mags are one of those magazines we read from front to back.
iPad/iPod: it's the 21st century, we don't go anywhere without these items and the plane is no exception. Some airlines have wifi so you can entertain yourself easily with either of these devices. Just make sure you download any games or books in advance.
Snack: Don't fall victim to purchasing expensive snacks on board. Pack a few of your favorites but don't be that guy that packs a tuna sandwich. Stick to chips, cookies, or trail mix.
Light Sweater: Don't act surprised, it's ALWAYS cold on an airplane. Be prepared and pack one that can easily be rolled up and thrown into your carry on bag.
I know this is called Top 5 but in addition, I also reccomend packing a small roll of duct tape. You just never know! I learned this the hard way when I took my luggage out of my car and while I waited for the shuttle bus to take me from the offsite parking lot to the airport terminal, a water delivery truck ran it over and busted it open. I know! I couldnt believe what had just happened. Thankfully, the parking lot had some duct tape but if it werent for them, I would have been in quite a pickle considering I was just starting my vacation.