Don't say Don't

Don't say "Don't"!

Stay positive with your student. They don't know what is right. Show them, teach them instead of criticize them.
Avoid using "don't" because you will confuse them. Try to tell them what to say and how to say it instead of pointing out their mistakes which they don't know how to correct.

Have a look:

Example One:
Student: I go museum yesterday.
Tutor: Don't say "go" if you use "yesterday". It's past tense.
Student (confused): Sorry?
Tutor: Don't use a verb in present tense when you say "yesterday".
Student (still confused): How can I say?
Tutors: It's "I WENT to the museum yesterday"
Student: Oh I see, I went museum yesterday.
Tutor: Be careful! Don't skip words. You should add "to" and "the". Say it again.
Student: I don't know...
Tutor: I went to the museum yesterday...
Student: Oh, I went to the museum yesterday.
Tutor: See what I mean? Do this next time.

Now compare it to Example Two:
Student: I go museum yesterday.
Tutor: Oh I see... You mean you went to the museum yesterday.
Student: Yes, you went museum yesterday.
Tutor: "I went TO the museum yesterday" (slowly)
Student: Yes, I went to...
Tutor: ... the...
Student:... the museum yesterday.
Tutor: Very good! What did you see there? and so on...

I think the difference is pretty obvious. Unfortunately I have heard the second example quite often.

Try to be more sensitive to your students' needs and learning style.