The easiest way to achieve true black print is by using "plain black" or 100% black ink. The color combination is: 0 Cyan (C), 0 Magenta (M), 0 Yellow (Y), 100 Black (K).
You can also create a "rich black" by utilizing the other ink colors. There are a variety of possible ink combinations, but the most common "rich black" is: 63 Cyan (C), 52 Magenta (M), 51 Yellow (Y), 100 Black (K).