The maximum size you're allowed to carry with you is a bag that is no longer than 45 inches in combined length, width and height. The bag, suitcase or luggage piece must be no longer than 22 inches long, 14 inches wide and 9 inches tall. The goal is to store these items in the overhead bin compartments near your seat. In addition to your one carry on piece of luggage, you're allowed to take one personal item. This can be a small backpack type of purse, a purse, briefcase, laptop bag or a tote bag as long its combined measurements do not exceed 36 inches total in its length, width and height. Outside of this, you are allowed reading material that may be in your hands, coats, a small bag of food, a pillow or a blanket.
The standard TSA "3-1-1" rule applies to the American Airlines carry on requirements when packing any liquids or gels. You may take liquids or gels in 3.4 ounce containers, which is equal to 100ml by volume. Your best bet is to either take travel size or sample sized items of toiletries found at local grocery and retails stores or to use bottles that specifically are marked "TSA" or "Airline" approved. Each passenger is limited to 1 quart-sized, clear, zip-top plastic bag filled with these containers. These plastic bags need to be placed separately into the screening bins when you pass through security.
Umbrella strollers are allowed as long the child that is flying with you has a paid ticket of her own. Wheelchairs, CPAP machines, walkers and canes are allowed on board. (ref 1) People with special needs are boarded first at departure time. Larger items such a guitars or other musical instruments may be allowed on board as your one carry on item, as along as the flight is not full or the airline crew can store it in the on-board crew storage. If this is not the case, it is at the airline crew's discretion to check the guitar or musical instrument at the gate. You can pick up the musical instrument at your arrival destination.
