So you want to learn how to draw unicorns. Well, you've come to the right place. I have been a professional illustrator of unicorns since 2007, and have been an appreciator and collector of these magnificent beasts since long before that. What I'm saying is this: I'm pretty much the best person to teach you how to draw them.
I'm not going to twinkle-toe around it, because I want to get straight to the good stuff. And by that, I mean creating magic with pen and paper. So here we go:
How to draw unicorns
No superior work of art ever resulted from a lackluster state of mind. So before you get started, you have to get inspired. There are a few sure-fire ways: surround yourself with unicorns you love, read this post about hipster unicorns, watch Planet Unicorn on youtube, or rent The Last Unicorn.
Now that you're fired up, grab some supplies. I am demonstrating simply using a sharpie with pink construction paper, but you can feel free to use whatever medium makes you happy. I have yet to discover how a tiny naked baby can assist in the unicorn-drawing process, but I am a believer, so I am sure that one day I will learn.
Oooh, ooh, ooh. Now that we're suited up and insprired, it's time to get drawing!
You'll start with the horn. It's easy, really: a thin, tall triangle with stripes for the ridges of the horn.
Now, add little ears on the sides of the horn. You want your unicorn to be able to hear the clatter of cupcake tins that means you're getting ready to bake, don't you?
Now, extend the face, adding two little "knobs" on the side for nostrils. You want your unicorn to be able to smell it when you bake cookies, don't you? 
Now for the biggest and possibly scariest step. Draw a long line which starts at the ear and cascades all the way down in a wave, forming the unicorn's back and the back of its hind leg. Whew! 
Now, starting at the bottom of the middle of the unicorn's face, draw another line--this is the front leg. 
In the space between, draw a total of 4 legs. Be sure to add hooves at the bottom, otherwise your unicorn's feet will be too sensitive to prance about. 
Oh, goody! We've reached what I personally consider the funnest part of drawing a unicorn. 
Add a mane, both as a little puff of hair in front of the horn and between the ears, and a nice cascade of hair down the back of the neck.
Add a swingy tail, too!
Add two assertive dots for eyes. Finally, your unicorn can see your pretty smile! Now, add two lighter dots below, for the nostrils.
Be sure to add a heart near the unicorn's butt. This is a spot from which it draws power and magical love energy.
Hooray! Now you have a unicorn to be your friend and companion. What will you name it? What kind of adventures will you share?
Enjoy the magic of unicorn art!