Tote It: In addition to your carryon luggage, make your personal item an oversize tote bag you can easily slide under the seat in front of you. Place anything you'll be asked to remove at security into the tote, so it's easily accessible — think toiletries, laptop, etc.
Within the tote, pack a zippered clutch you can later use as a wallet or an evening bag. If you're bound for someplace tropical, the tote can also double as a beach bag.
Save Your Soles: Pack a pair of dancing shoes for going out and a pair of boots you can wear to a bar or a business meeting. The only other shoe you'll need is a comfortable sandal or flat which you can you can wear while you travel to save room in your suitcase.