Lips

So here are some quick and messy examples of how I draw lips. Please ask questions if you need clarification. Everyone has a different style and method of drawing so please don't take my word as gospel, this is just how I do it.

#1 when drawing any part of the face, draw lightly so you can easily erase what you don't like.
# 2 Follows along with #1, lightly rough out where and what you want the features to look like first before defining them...
# 3 the lips will be centered under the nose so I suggest you sketch the nose first.
# 4 The top lip sticks out farther than the bottom lip in most cases, the lobe of the lip (the main bump of the top lip) sticks out the farthest and then the lips curve back and in to the cheeks. The top lip appears darker then the bottom because it is being shaded by both the nose and the bottom lip.
# 5 When I draw bottom lips I just use the lower line of the top lip as the top of the bottom lip an then add a shadow line where the bottom of the bottom lip would stick out farthest...I do not completely draw the entire shape of the bottom lip...unless the character is wearing lipstick

Keep practicing and remember that lips are not flat but rounded and curved, half the battle is learning where the shadows go. There are some awesome tutorials on DA about lips, search them and you will find a wealth of information on how to draw them.