Page navigation

Hi,

I am building a site locally using MAMP and I have several pages set up as templates with which to view categorised posts, I list 12 posts per page and need to set up navigation so that viewers of my site can see the other posts beyond the 12 on the first page. Ideally I want to add the php code to my templates so I can control each page template.

How do I find out the page ID of post overflow pages e.g for all the posts beyond the 12 I show on the first category page.

Can anyone help please?