Pack extra plastic bags. They come in handy for wet clothing and potentially leaky bottles. Small zip lock bags are also handy for keeping track of small items. Only pack what you can do without or include it in a carry-on. Leave valuable at home.
Many drugstores sell toiletries in trial size - perfect for a short business trip.
Less is more. Pack wrinkle-free clothes that mix and match and can be worn in layers. You might want to try walking around the house to find out if you can carry the bag for the long haul. If space does not permit, you may have to check a carry-on. So remember to label even carry-on bags with contact information and be prepared to transfer valuables.