I use a primer before applying my eyeshadow everyday. Primers smooth, conceal, and create a velvety base, so anything you apply on top will immediately look better.
I usually use Smashbox photo finish lid primer, MAC paint pots, or concealer to prep my eye lids for eyeshadow. Using a primer helps reduce the incidence of eyeshadow getting trapped in the crease of your eye lid and helps the shadow stay on for a longer period of time. A primer also evens out the color of the lid, ensuring a uniform application of color. You can even wear the primer alone if you have chosen one with shimmer, for a bare and beautiful day look.
My favorite MAC paint pot is the color Bare Study, which is a pretty beige color with flecks of gold shimmer. It compliments any skin tone and goes with any color you apply on top. Worn alone, it leaves just a hint of sparkle and shine on the lid, for that fresh faced look. No matter which color you choose, you will love the way it looks on the eye and how much time is saves you from reapplying your shadow throughout the day.