Crochet By Numbers patterns are often worked with an H hook and are done in single crochet. As for the yarn you can use any brand you wish but you must make sure that the color is correct. Of course you can change the colors to something else as you wish but you need to give them the correct number based on the pattern so your picture will turn out correctly. It should be noted that the CBN method uses the cut and tie method to change colors. These are meant to be one sided projects. But I do believe that you could carry the yarn or use bobbins and get a cleaner back if you desired.
Attachment is Paul Newman pattern for those who would like to try a larger project after learning the method and completing at least 2 of the training patterns.
Mod Note: Contains shorthand pattern only for Paul Newman.