Imagine when you're getting your picture taken. You want to look nice on the picture, so you won't stand like a log. Same goes for Illustrations. Always make the character you draw lively and interesting. That way, people won't find your drawing boring.
People look at a picture the same way they read - left to right, top to bottom.
If something catches their eyes, they will focus on there. We call that the focal point. From this focal point, the artist will direct your vision to where he wants. Catch the viewers' attention and direct them through your illustration. Here, Tang wants you to read this text, and my job is direct you towards it.