Even students whose tones are good enough to pass a diagnostic test (such as Laokang Tone Test) will slip up in conversation.
Outside the classroom “Laokang Tone Trainer” can help, but in class, or with a tutor, you are welcome to use this chart of the 20 tone combinations.
I use it in my class for drill, but more often for correction. For example, if a student reads 美国 as “mei2guo2″ (instead of “mei3guo2″ as it should be) I will say, “I heard you say this [pointing to 2-2], but I want to hear you say this [pointing to 3-2].”
I use the pdf version to project this chart on the screen in my “smart classroom”, and point to the relevant diagram using a laser pointer. When tutoring I just point to a printout. For a [free] poster size jpg file, please write me at: firstname.lastname@example.org.
Download the pdf (A4) here: