The issue is mainly that photoshop generally rasterizes text, which causes it to become unclear (especially at smaller point sizes and when antialiased), particularly when the text layer is rendered. Choosing clearer type and using it at readable sizes (10-12 point and above) is essential.
Otherwise, you can lay out all of your text in a page layout application (DTP - desktop publishing) like Quark, Indesign, or Pagemaker.
Thirdly, you'll want to work around 300dpi when working to print. Be aware that when you're looking at higher-resolution images on a computer monitor, they'll appear much larger than they will turn out because monitors can only display 72dpi. You can change the resolution of your template by opening it, going to Image>Image Size, checking off the "Constrain Proportions" option, then changing the Resolution to 300.
~Ladi