Dear K.:
Good for you! I have 3 lovely, strong-willed girls. We started discipline at a very early age by ignoring and NOT REWARDING unacceptable behavior. You are not doing your child any favors by constantly satisfying their needs immediately. Eventually they grow up to be demanding and unpleasant adults. (I'm sure we've all met those types...) They are never too young to learn that a pleasant attitude goes a long way to making life much easier.
By the way my girls are 11, 13 and 18. I was called mean (and other things) because I did not respond to what I felt was unacceptable behavior in my girls. Now, my girls are polite, helpful and kind to others. I can usually count on them to help around the house with a minimum of grouching. Is it a coincidence?
Stick to your guns.....If you aren't strong enough to teach your child how to get along with others, the world will. And you know what; the world won't be as gentle as you will.
Best of luck and remember this is one job that you'll never get a dime for, but the benefits are the best!