Seems obvious, but I still see it a lot. I get the mail piece, scratch my head and go where am I supposed to put the address? The address block, indicia and return address all need to be considered in the design.
This is especially the case with postcards. The customer decides to cut costs by using a small post card, then adds enough copy to fill a 3 page brochure. The result — they leave me with a 2 inch address area! They then hand me a list with 80 character fields and want me to bar code it to save them money.
The bar coding just ain't gonna happen! I need about 3" for the bar code, and it has to be 1/2" from the edge and I need a little slop to allow for the piece moving back and forth on the ink jet.
At 10 characters per inch, an 80 column field would take up 8 inches, so even using a microscopic font it's going to take up over 5 inches! It would have to be cleaned up and shortened in any case, but it's going to have to be butchered to get it into that small of a space.