Amber,
These are great questions!
1. The entry form, or premium, can be found in several locations. Often a club will post it on their website, or you can check agilityevents.com. You'll need to select NADAC and the state the trial is in. You'll get a list of all trials in that state, and can find the trial you want. Download the entry form (premium) and fill that out. The trial secretary's contact information will also be there, and they are a wealth of helpful information! Make sure you find the entry deadline, and get your entry in before that.
2. You can enter your dog in either the Intro (if available) or Novice level, and don't have to complete Into before Novice. That said, for your first trial, I would recommend entering either the Intro level or a Beginner Agility Trial. These are great ways to get yourself started in Agility!
3. What you need depends on where you're trialing, the weather, and your dog. On a cool day (under 70 degrees) I will often leave my dogs in the car, with the windows down and shade cloth around the car. If that's not an option, you will need a crate to contain your dog, and a way to keep your pup cool - either crating inside or with a shade canopy. A nice slip lead is also a big help, and don't forget the treats!
4. An associate membership gives you a discount on the cost of registering your dog, free permanent height cards, and a number of other benefits. Membership is not required to register your dog, or to compete at NADAC trials.
Thanks for some great questions, and have fun!!
Murrelet Halterman