Endless Gameplay Help

I'm creating a game in landscape form, whenever the character gets mid-screen I'm trying to make the background scroll with the player for endless gameplay. How would I be able to do this?? This is my first creation so hopefully I explained it right... Thanks in advance!
Comments
http://www.deepblueapps.com/Deep_Blue_Ideas_Ltd./GSTemplateSLR.html
deepblueapps is a website run by Darren and Wayne. it has lots of very useful GSTools. They are kind enough to give free stuff sometimes and they actually have and endless runner template for free this will actually give you a jump start on this type of games.. You just have to email them requesting the free template.
Hope that helps.
Steve