How do i get the page to center properly without sitting there and guessing until it looks good? With that in mind how do I make sure it centers in Internet Explorer and Firefox?

Put your layout inside a main "wrapper" div if you haven't already.
Then, on that #wrapper, in the CSS add this:

#wrapper{
width: xxxpx /* has to have a width defined, use em % or px*/
margin: 0 auto; /*sets top and bottom margins to 0, left and right to auto */
}

That works for the more standards-compliant browsers. To make IE center add this:
body{text-align: center;}

Then you'll have to add text-align: left to your #wrapper to re-set the text.