When you are designing a page layout in your own program (i.e. Photoshop), make sure you allow a 2mm space around the edges for trimming. Never place text against the edge of a page or thin borders because they are likely to be lost in the trimming process.
It pays to design your layouts as two pages spreads with printing in mind. Make sure you keep your text out of the binding edge in the book, as it can be difficult to read if too close. A 5mm allowance should be enough for the binding edge.
I know it can be difficult to remember this when you are scrapping, but it will save the hassle or disappointment later.
If you don't feel you have enough layouts to make a book, or haven't designed two page spreads. Here are a few tips that may just help you put a book together sooner.
Use only one layout per leaf and have a blank page on the opposing side.
Use wordart on the opposing side
Use similar pictures only or a simple layout on the opposing side
Write a poem or story for the opposing side.
Design a full page with a full bleed (right to the edge) photo only. These tend to have a dramatic effect and get a lot of comments for friends and family looking at your book. Simply design your page either square or A4 and it will fit into the first 'full page" template in the Photobook Designer software.