I like to break down ponies into shapes when I draw. :3 I always draw a circle for the base of the head so I don't make them too large or too small, same with the body proportions. I'm pretty sure you've heard this plenty of times but; practice makes perfect! I've surely improved a whole lot from when I started drawing by drawing everyday. o-O That sentence bugs me. XD But my way might not work for everyone, find the way that works best for you. :3
To answer one of your questions, I mostly draw ponies from memory.
Tip **Also color in the dark black in the eye last, it helps it not smudge as much.
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Here's some helpful links:
http://twilightflopple.deviantart.com/art/Pony-Drawing-Guide-Heads-268211758
http://twilightflopple.deviantart.com/art/Random-Pony-Drawing-Guide-263679771
These should help.