Ubuntu – How to make Postgres start automatically on boot

I am new to Ubuntu and I would like to know how to make postgresql start automatically on boot and how to configure my setup so that I can start the postgres server if need be.

I am working on a small rails project and I have been having difficulties with postgres starting correctly. I have had to resort to uninstalling and reinstalling postgres to just get the project up and running just to get work done. I have been using these commands.

sudo apt-get -y update
sudo apt-get purge postgresql* # ending * is important
sudo apt-get install postgresql libpq-dev

from this post

https://stackoverflow.com/questions/17934055/postgresql-cannot-connect-to-server-locally

skipping

sudo add-apt-repository ppa:pitti/postgresql

as it appears it is out of date and there's a comment below about not needing it.

If it helps my pg_hba.conf file appears to be located at

/etc/postgresql/9.1/main

I am running Ubuntu 12.04 on top of chrome os

Thanks all for the help and sorry for the newb question!