A Series is used for most types of general printing i.e. Stationery, publications, brochures and flyers etc. You'll see that all the sizes are in proportion to one another, with A0 being twice the size of A1, which in turn is twice the size of A2 and so on.
|A0||841 x 1189|
|A1||594 x 841|
|A2||420 x 594|
|A3||297 x 420|
|A4||210 x 297|
|A5||148 x 210|
|A6||105 x 148|
You should scan your images using a resolution of 300dpi at the final dimensions you intend to use them so that your colors will look smooth, and hard objects will look sharp. In other words don't scan at 300dpi and then enlarge the picture by 200% in your layout program! You should not use images that are lifted from websites; they are probably only 72dpi in resolution and will look very blurry if printed on a printing press.
Any time an image or a colour is printed to the edge of a page, the image or colour should extend at least 5mm off the edge so that when the page is trimmed on a guillotine, small variations in the trim will not result in a white line down the edge of the page.
When you want an area of solid black within the document, 100% black (K) is not enough; use Rich Black, which contains a CMYK mix of 220% as represented by C:40% \ M:40% \ Y:40% \ K:100%.
Always convert your Photoshop files to CMYK! Your files will be printed on a CMYK press. An RGB file may print correctly on your color laser printer, but it does not translate correctly on the RIP. Be sure to change your files to CMYK to avoid costly delays in your print job.
Always supply artwork as a high resolution pdf with crop marks and bleeds. No other files accepted. Ensuring all fonts are properly embedded.