How to avoid spoiling your child

How can my husband and I make sure that we don't overindulge our cute little girl? She has a wonderful sweet personality and everyone in the family has been doting on her since she was born. But now that she's four years old, I'm wondering if she'll ever grow out of this "cute baby" phase. She loves being the center of attention and will "perform" on cue if given the opportunity. Is this normal, healthy behavior? Should we be concerned? What, if anything, should we be doing differently?