1. Using web graphics on printed material.
With several young designers coming from a pre-dominantly web design background the transfer over from web design to traditional design for print can bring with it a multitude of design sins. Images supplied at 72dpi and crunched down to load fast on a website are going to reproduce very badly in print you can get away with small thumbnails but blowing things up to any exact size is going to be pushing your luck. There are a number of online sites offering free or very cheap quality hi resolution images which are a good source for suitable imagery.
2. Forgetting about or not permitting enough bleed.
A very common error is to send to print a document or flattened image that has no bleed at all. Usually speaking you must permit at least 3mm around every cut off edge. Failing to do so will give the printers no leeway and will either crop off the side of the page or give you a white border. It is always a good idea when supplying image files to save layered PSD files then if things require extending or cropping you can do this on the background layer and hopefully cut down your work
3. Using obscure fonts and not embedding or outlining them for output.
We’ve all been guilty of this at some point and things are usually fine if you are going to be the only person accessing your artwork or documents. However if someone else needs to amend the files or use your vector logo on one of there publications. Unless you package up the used fonts, they are not going to be able to open the files correctly and some software programs may replace any unknown fonts with a default. This is a specific problem when you require digging out stuff that was made many years previously and you no longer have your old fonts installed.
4. Supplying print ready artwork using spot colors or rub
There are valid reasons for using spot colors in artwork, logos that need to reference specific pantone colors for example. In general design work however most print is sent through on 4 colour presses CMYK with occasional 5th colour for luminous or metallic colour or for spot UV varnish. It is very common for lazy designers to just place rub images into files and expect the vibrant colors seen on screen to reproduce in print.
5. Permitting design illiterate customers to lead you round the houses
The customer is always right, goes the old adage. However it is often said with gritted teeth and a sense of patience that recognizes that these morons will at some stage is handing over a fat cheque for your troubles. It is often a good idea when first submitting visuals to throw in a couple of stinkers to hopefully get them to exact the design you would like them to accept. There is the very real danger of course of them loving the piece of absolute arsenide that you knocked up in five minutes to make them think you’ve been earning your money. Still it’s a living.