Lots of stuff is done on the computer, so rulers aren't really so common. Maybe the line tool.
As you get better, you start being able to eyeball your vanishing points and stuff so you don't need to put all those lines in there. But until you CAN you need to. Don't NOT use them just because advanced artists don't. It won't make you good, it will make you bad. You can't skip steps
For books, anything about animation. I like Chris Hart personally. Disney also has at least one really good animation book.
I usually draw foreground figures first and then add in a background; sometimes I draw the grid first and then place the characters inside it. There are plenty of books about animation. Amazon.com shows reviews and ratings.