One calibrates a printer by sending it "known" values, such as RGB values, in the form of patches, which your printer prints out. These aren't an image, but are generated at the number level so the values are understood by the software. Then you read in the series of patches using a spectrophotometer and the software creates a model of the differences, a curve to imagine where all the other thousands of colors will fall, etc. I generally print out about 5,000 patches to create a profile. (That's after doing a linearization.)
I don't' think monitor calibration is as important, I think its mostly about a clean gray. However, I have a good monitor and I do it regularly. I'm sure it helps a little. There are services which will send you a sheet of patches to print, then you send it back and they read it and send you a profile. Chromix is one such company I have used in the past, before I had my own profiling tools. The tools are expensive, and the software isn't easy to learn. Unless you plan to master it its cheaper to hire a service, at least for your favorite papers.
If you are printing things out at a store, without using a profile they supplied, then the success you have had is a matter of pure luck. By the same token, if you print something out on your own printer and its too yellow, open up photoshop, or whatever editing program you use, and make it more blue until you like it. Printing on ink jets is the same as printing in the darkroom. First you make a print, then you look at it and if you can make a better one, you adjust and do it again until its just right.
Sometimes it takes two tries and sometimes it takes 30.
Lenny
EigerStudios