In my case, during school I knew that the local children's hospital was where I wanted to be after doing my clinical hours there! I kept my grades up, worked hard, and when the time came for our preceptorships - I was awarded one of the two in the hospital. I then spent the entire 80 hours or whatever it was acting like I was on the most important job interview of my life. :) I worked hard, I learned SO MUCH, and when the time came - I connected with the managers of the unit where I had worked and kept in touch.
When I graduated, the unit where I had worked did not have a position available - but they sent my information and good words up to another floor... where I interviewed and was eventually hired. :)
In my area, each floor has an "allotment" for new grads, they can only have so many because they are expensive to train. So you have to dress to impress, so to speak.