I live in a small town, where your choice of printing photos is Wal-Mart or Walgreens...soon will have a CVS available when construction is completed.
I use Walgreens, because they have a 1-hour service, and will make glossy prints. Wal-Mart offers matte for 1-hour service, and I prefer glossy.
I have found out that Jake is correct in stating that what you see on your monitor is not necessarily what you will see on your print. Everything, not just color. Contrast, cropping, and all the other things that you so carefully edited to get your image just the way you like.
What I have done is figure out what the "Photo Lab" does at Walgreens or Wal-Mart. They have software that automatically adjusts the photo file that you submit to them, either off a CD, card, or through the internet. Cropping is preset, and they do not re-size it like you would. In other words, they make changes to what you give them, in hopes that they will give you a great print, and you will come back and spend more money with them. (My guesses from what I have seen...)
At my Walgreens, it costs me 19 cents for a 4x6 print. I have learned to lighten my images just a tad, and to give my images a white border. Thus, I send in the image that is about 95% of a 100% image... The white border takes care of their cropping, so that I still have the entire photo I sent, and the very light adjustment they give the image is taken care of by my lightening...hope that all makes sense...
In other words I have experimented with what I send, so that I get back what I want. I really don't have to make big changes, and I automatically know what to do with images I transmit to them from my computer. So, for 19 cents I can preview my image, or use them to figure out how edit images to send to them. And, I like the instant gratification...usually in 30 to 45 minutes I have my prints.
Walgreens also has an option for you to transmit a high resolution file to them, and they will not make any of the changes that they normally would to produce a print. This is what I use. It is slower, but the results are much, much, better, IMO. Minor changes are still applied to the image... I think Wal-Mart has, and does, the same thing.
You may already know all of this, and I apologize if I duplicate information here.
I have not had anything printed bigger than 8x10. I have had really excellent results from Walgreens here.
I am sure there are members who work at Photo Labs that could give you further tips about their service, and perhaps they will lend a helping hand.
I have learned that printing is a whole 'nother world in the Photography Universe...and I have a LOT to learn about it!
Have a Great 2013!