Add the $10 pp/per day tip charge on your onboard account. This eliminates the need for divide up the cash into each envelope at the end of the cruise and it helps the staff keep their tips. If someone goes above and beyond you can give them extra in a separate envelope.
Don't deny yourself the chance to sample the local food just stay away from the local water, ice and fruit. Drink bottled water, boiled tea, coffee, soda and beer. Also make sure all foods are well cooked.
In over 100 ports I have yet to be inspected for fruit or food but I would advise that you do not bring anything that contains mayonnaise, cheese or any dairy product, just for safety.
When going ashore only take what you need. Your ships card, one credit card an ATM card a small amount of cash, a copy of your passport and/or a photo ID. Use your credit card for larger purchases and if you need more use the ATM.
Also have an emergency $50 and the cruise line's shore representative's number and address tucked somewhere in case you need it. Pinned to the underwear or in the bra is a great place.
Plan your excursions BEFORE you go on the cruise. Nothing ruins a day in port worse than getting off and saying "What do we do now?" You only have a few hours, make the most of it. Unless you are the type that enjoys that sort of thing.
Don't try to do everything: Leave time to relax.