Carnival pros cut off the toes of their tights, then they wear their tights like a spandex pants that ends just above their ankles.
Wear comfortable and preferably well worn-in sneakers. Lets face it, you need shoes that are designed for running, jumping and walking long distances. Shoes should fit snugly but not be overly tight. Don't be seduced by suggestions to wear flip-flops, sandals, boots or heels, especially if this is your first time playing mas. You will be on your feet, marching, for 2 days.
Get creative; turn your old sneakers into distinctive Carnival footwear. Decorate your sneakers as a craft project, using your costume colors and design as reference. If you register early, you'll have lots of time to shop for sequins etc. to make your sneakers uniquely you.
A good way to rejuvenate your feet, on Carnival Monday night, is to soak them in warm water and bicarbonate of soda. It is like a mini hot tub for travelers and surprisingly effective.
The second most common side effect has to do with "chipping", the standard, shuffling dance step of Carnival. While chipping is the most energy efficient gate for Carnival, it sometimes can have a minor side effect.
If your shoes are worn loosely, this marching shuffle tends to jam your toes into the front of your shoe. The result, for those with long toenails, can be bruising and loss of the big-toe nail. The easy way to prevent this, is to simply clip nails as short as reasonably possible prior to Carnival, they soon grow back.
Pace yourself where alcohol is concerned. While it may be a novelty to consume alcoholic beverages in public, you probably will not want to get so tipsy - really drunk - that you become a problem to those around you. Remember, Carnival is 2 days, so you'll probably want to make the most of your experience and enjoy both days to their fullest.