Colours
Commercial printing uses the colours to be produced by the CMYK procedure in your leaflets and this involves using mixes of Magenta Cyan, Yellow and Keyline Black. As you may have found this is not the same as the process used to make the colours on your display which uses a mixture of Red, Green and Blue (RGB). This indicates that, in most cases, the colors you use to produce your leaflet on your own computer screen will turn out otherwise to the colors printed ultimately on the page, the exception to this is if you have a correctly calibrated and colour coordinated monitor, but unless you're a professional designer, that's highly improbable!
If you're employing a layout program that can use CMYK, for example Adobe InDesign & Photoshop, Microsoft Publisher, Quarkxpress, Scribus etc., you might get nearer to the colors of the final print.
Some companies add profiles to your own RGB artwork to get the CMYK values as near as possible, however they will not ever be as vivid and lively as they are on an RGB back-lit screen.
Bleed
A crucial concern when leaflets is including bleed along with your design/art. Bleed is utilized when text, a colour or graphic will be printed right around the clipped edge of your leaflet. It's essentially an area outside the normal size which can be trimmed off to leave no blank paper whatsoever. That is a result of the small movements of one or two millimeter when trimming a large stack of paper using a guillotine, to give the final result that is most effective.
Different printing companies function with somewhat different sizes of bleed, but 3mm is a decent excess to depart. For example then, an A5 leaflet which is usually 148x210mm must have a a full page dimension of 154x216mm, incorporating 3mm to every border.
It is also worth making a space between the region as well as the clean-cut line where your leaflet advice is, not simply to make sure it can not get trimmed, but having text too near the edge can look unprofessional and a little haphazard.
Resolution
When sending your art to commercial printers, it is necessary the resolution of your art work is high enough so that when printed it's sharp and clear. Your standard internet pictures seem excellent when viewed on a monitor, and are 96dpi or 72, but try and get these printed out and you'll see the enormous difference in quality.
High res PDFs are marginally distinct, as fonts are often embedded, hence the document doesn't have an overall resolution. It can be determined by the settings of every bundle, but pictures in PDFs should often be exported as any industrial print settings and at least 300dpi should be selected, as above using CMYK and the PDF should subsequently be OK to print from with bleed.
Time
More significant than anything is time. Chiefly because the other suggestions, even if ignored, can all be corrected, provided enough time. It is impossible to leave lots of time, but an extra few days to provide the printer an opportunity to flag up any problems, providing you with time to correct them, can avoid reprints and costly errors. It also gives you opportunity to go through your proofs with less stress, which makes it more probable you can spot any glaring errors.
