I enjoy the crowds at theme parks and consider them as part of the entertainment. However, if your goal is to do more than just people watch in the culturally diverse fishbowl that an internationally famous themepark provides, you need to plan your visit carefully for optimum enjoyment.
I have found that the most important aspect of visiting a crowded theme park is timing. The heat, overcrowding and pressure to do everything to attain full value out of the admission price is multiplied by the thousands of guests also trying to achieve the same goal.
Your number one concern should be your OWN enjoyment.
Relax, HAVE FUN, or Go Home.
If you arrive when the park opens you can see and do a lot before everyone else arrives. If you are a vacationer and are staying nearby, don't be afraid to leave and return later in the day.
My favorite time at the parks is both opening and closing. At Opening you have your excitement of waiting to enter to add to the themepark experience and at closing you can relax and leisurely stroll through the empty park as the park attendees herd you out. I have gotten the best themepark photos after the park has officially closed and have had themepark landmarks unobstructed for our own amateur souvenier photos.
Don't let the crowds get you down.
Roll with the flow.
Don't try to do everything, only what you leisurely can. If you miss something it will not compare to the grief that you will put yourself and family/friends through trying to visit everything Commando Style.
Crowds will be there when you want to go but that's because everyone else is also restricted by the scheduled off days that the Holidays provide.
You are already getting a jump on the competition by planning ahead and visiting websites like this. Don't be afraid to also buy a book or two from your local book store and read up. These "Unofficial Guides" are also great carry alongs to bring with you on your visit to make last minute modifications to your themepark visiting strategy.
Most importantly is to...
HAVE FUN