kablam comics lets you print cheap and no minimum bulk order. (unless its in a manga size which your min. order is 2)
Convert your files into cymk. this is because a computer and a printer uses different methods of creating color. A computer uses rbg or red, blue, green light to display color, a printer uses cyan, yellow, magenta. (K- stands for keytones, but that is another topic) When converting to cymk don't be off-put by the colors getting lighter. that is normal, and 9/10 you art will print just fine, because the printer will mostly likely print you art much darker. (always seems to be an issue at school. DX )
Next what ever printer you go though, make sure you you format your files in a way they as you to. If you don't, it's not the end of the world, but they may charge you extra money for it.
If you can get a test print from the printer it helps to see how their printers print your colors and you can adjust accordingly. Most print shops have their printers set slightly different because there is no standard for whatever reason. unless you print in pantones. (another topic for another day, just know professional companies will pay hundred or thousands of dollars for the perfect color every time and purchasing the use of a pantones. not that it would cost you for personal use, professional companies are more likely to use that)