Before We Begin
Baking is an art, but it's a technical art. There are definitely a couple different ways to get beautifully frosted cookies, but, in my humble opinion, some ways are better than others.
For starters, you'll obviously need cookies. Google "cut out sugar cookie recipe" to find a top-rated one that suits your pantry. Make sure they're baked throughout (not soft in the middle, as crave-worthy as that is) and ensure they cool in a dry, non-humid environment. Taking these extra steps will ensure your icing does not get dark blotches, or "butter bleed" from the cookies.
Now on to the decor. Called "royal icing," this easy-peasy frosting is comprised of only three ingredients: merengue powder or egg whites, powdered sugar, and water, all whipped up together (recipe here). All you have to do is combine everything in a bowl and turn on the mixer—as all the tiny pockets of air start getting incorporated you'll watch it go from a gray sludge to glossy, sugary perfection in a matter of minutes. I prefer using merengue powder over egg whites for several reasons: it's safer, the measurements are more precise, and leftover frosting made with merengue powder can be stored in your cabinet and reused for up to a month!
As for dye, the four-pack of food coloring probably lying in the recesses of a forgotten shelf could work, but go the extra step and buy gels instead. They're not expensive (Wilton's 12-color pack clocks in at $12.51), and there's a few advantages: the color will be more intense, you need less of it, and because it's gel, you won't have to worry about the dye watering down and changing the consistency of your frosting.
Then there's the business of getting the icing on the cookies. A traditional icing bag will do just fine, or if you're in a pinch, you can make a temporary one out of parchment paper or even a Ziploc bag. However, I find icing bottles are the way to go. They not only ease the learning curve when it comes to decorating (they make you feel like a pro in no time!), but with caps that screw on, it's a cinch to store leftover icing. The set by Fox Run above includes three bottles and will only set you back $5.99. Can't wait for your order to come in the mail? Most of these tools can also be bought in craft stores like Michaels and Jo-Ann Fabrics.
Lastly, grab yourself some toothpicks. Trust.