This is from an all-day spectator perspective:
DO Bring jackets/blankets. The arena is super air conditioned usually, so it gets very cold (especially when everyone is dressed in shorts for "Florida weather". Just because its 90 outside does not mean that is the case inside!
DO Plan, plan, plan. If you think that you need to get on a bus 20 min early at the hotel, go another 20 min earlier. All 3 events are very fun but can get very busy, especially worlds, and especially to/from allstar resort as that is where most people stay. I stood in line from 7am until they slowly started letting people in the arena for worlds-Sunday (Large senior was at 9am) and did not leave my seat until 10pm. I went with 1 other person and we tag-teamed holding our seats if one of us needed to use the bathroom. We also brought a big backpack with seat cushions, a blanket, and a ton of snacks because we knew we were in it for the long haul.
DO bring your own food. There's really only 1-2 food places open at WWOS, which = long lines during breaks (like every cheer comp) & not a huge selection of great food. It's alright for a snack or some chicken nuggets but that's about it. I recommend at least packing some snacks or sandwiches, so that even if you buy some food, it isn't everything you eat.
DONT wait until 20 min before a division to find a seat. I have seen my fair share of kids sharing a seat/sitting on laps, etc. & we are talking 3 kids to a seat at worlds. Also, DONT try to stand/sit in the aisles. It's a fire hazard and they will make you to move (politely the first time, not so politely after that). Again, @ worlds this was a big problem. A few times they refused to start divisions until people complied with this, because people were clogging up the walkways. I always feel awful for the Disney people that have to constantly deal with this........tough job.
From a competitive aspect:
DONT tire yourself out at the parks before competition weekend. The Disney parks are awesome, but are a lot of walking. Making your legs/feet tired the day before you compete or staying up playing around in Magic Kingdom until 2am is not smart. You are there to compete, so competition = 1st priority, fun time @ the parks = 2nd. There will be plenty of time after you compete to see everything.
DONT go to the pool or parks without sunscreen. Getting burnt on comp weekend = not fun.
DONT try & stunt in the parks. Everyone wants that lib picture in front of the castle or the epcot ball, etc etc etc, but it's a liability for Disney and makes them really nervous. All that path under those landmarks = concrete! When I interned there, they were telling all the photopass cast members every cheer comp weekend to ask people to get down if they were stunting due to safety (not only for themselves but the guests around them....those spots are highly populated usually). People still do it, but its frowned upon.
DO expect to not get much sleep. Lots of cheer competitors all in the same hotel = loudness. Disney tries to keep it managed the best they can, but its a lot of teams and not a lot of people listening usually. I suppose you could always bring earplugs or hope your surrounding teams are quiet/leaving for comp around the same time as you in the morning so they will be asleep at the same times.
From a Disney park perspective:
DO use extra magic hours.
DO leave early before the parks open to make the most of your park days.
DO plan out what you want to do & DO get fastpasses for highly busy rides (Space/Splash/Big Thunder, then Enchanted Tales w/Belle, then Peter Pan or Winnie the Pooh = MK....
SOARIN' then
Test Track = EPCOT.....
TOY STORY MANIA, then Rockin' Rollercoaster then Tower of Terror at Hollywood Studios.....Expedition Everest then Kilamanjaro Safaris at Animal Kingdom. Underlined ones will be 2 hour waits unless you fast pass or ride right at park open)
DO get in line @ 10:30am to eat lunch at Be Our Guest in Magic Kingdom
DO get lots of delicious snacks in the parks (Research on the DFB:
http://www.disneyfoodblog.com/ I recommend a Dole Whip Float ( Pineapple soft serve in pineapple juice) at MK...... the strawberry shortcake @ Sunshine Seasons, School bread from Norway, Fresh caramel popcorn or a caramel chocolate apple in Germany(ask it to get sliced), a Primavera smoothie in Italy, Kaki Gori (Snow Cone) in Japan, or anything from boulangerie patisserie in France for EPCOT (this is delicious food central. Eat here as much as possible!).....A giant cupcake from Starring Rolls @ Hollywood Studios......A Jalapeno Cheese pretzel from the cart by Kilimanjaro Safaris or the White Elephant or Cotton Top Tamarin Cupcake from Kusafari Bakery @ Animal Kingdom)
DO make reservations WAY in advance for anything special if you want to do them (Sit down restaurants, Bibbidi Bobbidi Boutique, etc.)
DONT wait to buy something until the end of your trip. It might not be there when you come back. Also, some things are park specific and will only be sold at certain stores. Downtown Disney does not sell everything (contrary to many people's beliefs), so don't count on them always having it, especially if it is specific to a ride or the theme park. Save yourself the trouble and just tell them at the register you want to ship it back to your hotel (it's free and will be waiting for you at the allstar resort merchandise shop the next day! Win-Win).
DO have your ID on you if trying to use a credit card & that card is not signed.
DO bring a cheap poncho for everyone in your family. $1 from walmart> $8-12 from the parks & = life saver in random spring showers (or on Kali River Rapids....you're gonna want the poncho for that ride for sure!!). Florida is very rainy in spring time and a 1 hour rain storm will come out of nowhere. Once that passes, the rest of the day it will be perfectly clear again.