fill your bathtub with water if you have one, great for flushing the toilet.
fill everything you can with water/check your tinaco to make sure it's full
bottled water
money as the bank machines will be down or empty of cash
first aid kit
BBQ with a full tank of gas if you don't have a gas stove in your place
Charge your cell phone and all of your electronics, we had email 2 days after Wilma which was great to let everyone know you are ok.
batteries
flashlights
bleach
mosquito repellent/deet
hand crank radio
I put zip lock baggies on the legs of all my wood furniture in case of flooding, it works really good.
Don't drain your pool as it will still fill with rain water + all of the debris which will then clog your drains and plug it all up.
I could think of more I'm sure but I am wishing it all away this year. Emily and Wilma were enough for me and I am just too busy for all this