With any product that has been through a design process and manufactured, the end result is more than meets the eye. To make the execution successful the initiation need to be correct.
Print Design Steps
All printed products have a few steps to go through, from start to finish. In the first phase, after a thorough brief, a graphic designer sets up the artwork. As a graphic designer, in this process there are a few important things I keep in mind planning my design. It is so much part of the design as it is necessary for the final important finishing phase. In most printing processes there is a finishing phase at the end.
I find the 3 following elements important to consider as part of planning the design:

Bottom corner of a page with cropmarks. Guidelines for a margin on the inside, edge of the page and 3mm bleed.
1. Bleed
In a nutshell, especially with large quantities and thick brochures, extra (usually 3mm) material all around the edges are required for the finisher to trim the paper. If the page has a printed background it avoids the possible white edges. Read Sam’s blog post What is bleed and how is it used in print? for a more in depth discussion about bleed.
2. Borders
Moving a bit inwards and there is a border involved there are a few things I keep in mind for my design. Adding a border to a page/design, the idea (most of the time) is to have even thickness all around. All is good and well if you have an A4 page with a border that is 10mm from the edge. It is lenient to the finishing process trimming a stack of paper and to have 0.5mm to play with. Any slight movement will still be unnoticeable to the eye.

The left side is more lenient for trimming. The right has a 3mm border, where 0.5mm will make a difference.
Compare the previous example to, for example, an A6 card. If it has a 3mm solid border right to the edge, 0.5mm will not be so lenient to the trimming and neither to the eye.
As part the design it takes a bit of judgment when using a border. Keep finishing in mind and consider the finished printed size of the project and what kind of border is being used.
3. Margins
Moving further inwards… When planning a design for print, margins and grid is an important foundation to an end result that is organised and pleasing to the eye. Especially when designing a brochure, the size of the outside margin of the page is important for page elements such as page numbers.
Printed page spreads for a brochure are placed in sequence on top of each other (cover on the outside and inside pages that follows). It gets folded in half and stitched to be trimmed. The fold makes the pages appear a little bit bigger as it goes from the most inside page to the most outside page – almost like little steps. To avoid the finished brochure to have little steps for edges, this needs to be trimmed to even edges. If the brochure has page numbers in the left or right outer margins too close to the edge, it might come across that the page numbers are moving closer to edge. For the best result I usually plan my page numbers to not go too close to the edge and preferably in the top or bottom margin of the page.
Read Tom’s blog post Book binding techniques for a more in depth discussion.