<p>Another good idea, perhaps, would be to say that, if the teacher can't give you a lesson, would he/she be willing to allow you to sit in on another student's lesson. My teacher at home is SUPER busy (he teaches at 5 schools! and is a principal player in a major orchestra), so a lot of times he lets prospective students sit in on his students' lessons if he can't fit in giving trial lessons. </p>
<p>Better than nothing!</p>