I just posted the code I use at the top of every IPython notebook to GitHub: https://github.com/masnick/ipython-setup
It was somewhat difficult to figure out what to import (and the conventions for this) when starting with IPython. This setup file takes care of that.
It also has some additional goodies like my code toggle button and my method to display raw HTML inline in the notebook.
In any case, I recommend standardizing the contents of the first cell in IPython notebooks, saving this out to a file, and then using %load magic to bootstrap the first cell. (This is explained in more detail in the GitHub link above.)