- Make certain you open any new document in CMYK color mode. Yes open in CMYK, don't switch to CMYK if you opened an RGB document by mistake. Many things in Illustrator are dependent upon the document color mode. The Swatches, symbols, graphic styles, brushes, are all built to match the Document Color Mode. Switching color modes mid-stream does not change these items. Only opening a document in the proper color mode generates library items in the proper color mode. If you have work in an RGB document and need to print it, Copy/Paste to a CMYK document and then adjust coloring as needed. Do not simply change the Document Color Mode.
- Turn on Overprint Preview in the view menu (if it isn't already on).
- Ensure Document Raster Effects setting (Effect Menu) is set to 300ppi
- Ensure all linked or embedded raster images are in CMYK format at 300ppi (as well as other Photoshop requirements)
- Ensure all blacks are accurate. Whether using rich black or greyscale black, ensure objects are correct. And for heaven's sake change the preferences to always display and always output blacks accurately. I dislike Adobe's default settings. They are a recipe for error where print production is concerned in my opinion.
- Ensure you have proper bleeds for any full-artboard projects.
- If using spot colors and transparency, stop. Don't. If you need transparency, then convert all spots to CMYK otherwise don't use transparency (other than clipping and opacity masks).
- For Illustrator-only projects it can, at times, be beneficial to simply rasterize entire artboards and save as a CMYK .tiff. This depends greatly on the artwork. However with really complex vector illustrations it can ensure printing is correct. Obviously when doing this you loose any spot color so it's only an option when working with CMYK.
- While not required, using Global swatches for CMYK colors can be very helpful. You can double-click a Global swatch and change its color build to change all colors in the artwork. This only works with Global Swatches.
- Use the Flattener Preview to verify the artwork will flatten as expected. You may need to expand appearances or flatten pieces of art on some occasions. I just recently had to rasterize a masthead to assit a print provider in outputting it properly.
- In general, Photoshop merely requires you to ensure the document is the proper resolution and the color profile is correct. If you've calibrated your system properly there's traditionally little more to worry about for straight CMYK projects.
- If using filters or items which require RGB mode, then work in RGB and convert to CMYK as the final step before outputting the image. This step is dependent upon proper color settings.
- For 6 or 8 color, or any spot color project there can be other concerns depending upon inter-application workflows. For example, if you are using Spot colors in Photoshop and also using those same spot colors in Illustrator or Indesign, you'll want spot color channels in Photoshop. This is so upon output all spots are on the correct plates. I won't go into the creation of spot channels in Photoshop since, that in itself, is an entire topic.
- If taking a Spot channel Photoshop document to Illustrator, you need to use the DCS2 format when saving so Illustrator can properly read the spot channels. If going to Indesign from Photoshop, you can use .psd, .eps, .pdf, or .dcs2.
- There are other things which may need addressed - color correction of photos is a big one, especially photos containing people. However I feel that too is a topic unto itself. There are tricks, for example, people should generally have 3% more yellow in their skin tone than they do magenta. This prevents a "rosy" appearance for people.
- ensure you have proper bleeds for images.
(Some of this relates to QuarkXpress as well)
- Again ensure the preferences are set to always display and output blacks accurately
- Placed raster images should be 100% and not rotated within Indesign. If you need to rotate an image or scale it, then note the degree of alteration, go back to Photoshop and apply those alterations and reimport the image. For optimum output all placed raster images should not be scaled or rotated. In all fairness, this is one of those items that has some wiggle room. A minor adjustment probably won't cause any real issues. However large scaling and rotations of placed raster images can effect the output of those raster images.
- Turn on Overprint Preview in the view menu.
- Ensure you have proper bleeds for pages.
- Always a good idea to run Preflight before exporting to PDFx. This will show any missing fonts or RGB images or other issues.
- Do not use rich black for small "body copy" text. If body text is black, just use 100% K. (this would hold true for Illustrator as well if you are using that as a layout application with smaller text.)
- Accurate color profiling of any system is imperative. If you accurately profile your system then you will traditionally see on screen what is going to be output.
- Ask what your printer prefers for rich black. Every printer is different. They will have their own mix fo rich black. Use that mix for black when needed. Side note: if you accurately color profile your system and the app color management is set up properly, you'll get rich blacks in many areas. These can be okay to use if you don't know your printer's mix. The printer can convert but maintain numbers if they know what they are doing. if they don't know what they are doing, any rich black is better than none.
- Get color proofs where possible, especially for large jobs or those 6 and 8 color jobs you asked about. Printers have moved into the "internet" age as well and will often want to simply supply online PDF proofs. These are okay to check for drop offs. However, you can't color-proof a PDF. Ask for a color proof or Chromakey if you feel color is imperative. They can be FedEx'ed overnight (yeah they cost a bit). They are well worth it for some jobs.
- Develop a good report with all print providers where possible. So many issues can be corrected by a simple phone call or email before a job is run. If the print provider knows you, he's more willing to stop and check than simply run the job and then re-bill when he has to rerun it.
- The mark of a good printer is not how well things go when there are no problems. The mark of a good printer is how things are handled when there is an issue.
I'm sure I've missed a thing or two but this is a general outline.
With respect to "test prints" there's really little you can do for many files. Unless you've got a very high end printer and you are creating files for digital presses, nothing you do in an office/home office is going to come close to a commercial platemaker and press.
I run prints through a simple monochrome laser printer (postscript level 3) to ensure alignment of objects if needed. Or to physically see text sizes rather than merely estimating based on the screen. Printing a page here or there can also assist in checking balance and readability from a distance. That's about as far as I go for "test" printing.
Each project is unique. It's difficult to give blanket guidelines for any "CMYK" printing.
If creating a booklet, brochure, or something which will involve die cutting and/or bindery I will make a miniature mockup in order to verify folds are correct and page placement is correct. Just bank sheets of paper folded and cut to match a scale model of the final piece. I then scribble on the pages of the mock up to indicate page direction and order.