question about wordpress splash page

This question is about a splash page.
I am using WP 3.4.1, and am hosted on hostgator, in case you ask.

I am defining a splash page as a page that a visitor will see when they first visit the site, and after that they won't see it anymore.
They will see the splash when they come to the domain name, or perhaps any of the pages on the site, but only once.
I have tried some of the plugins, read the codex at least minimally there...
I am pretty sure the plugins that say that splash pages are easy with their plugins - they are all broken - so having tried splashgate and wp splash ( any others please i will try them ) they are not very well supported.
So i think to be sure i can get it working i am going to have to go into the php files and add some code myself.
But where are some examples of this direction i need to take?
If you link me to a codex please make sure it is up to date and current and is relevant to the question.
thanks,
ed