Airline regulations change all the time in this post-Sept. 11 world. One day, your bottle of travel shampoo is fine; the next, it's confiscated for being over the size limit for carry-on liquids. Laptops used to be fine in the seatback pocket, too, but no more. The rules have changed, and now they need to be stowed under the seat or in the overhead bin when not in use, just like everything else you carry-on with you.
Save yourself the headache of learning the rules too late by checking the web site of the Transportation Security Administration and the Web site of the airline you'll be using to travel. The most up-to-date regulations will be there. Make sure to share them with your travel companions, too. It'll help keep hassles to a minimum.
Speaking of laptops, check out the next tip for a new way to spend your in-air time.