Ask questions -- Rikyu hyakushu

はじをすて人に物とひ習うべし是ぞ上手の基なりける
haji o sute hito ni mono tohi narau beshi kore zo jozu no motoi nari keru

Sometimes person may feel embarrassed to ask questions. That embarrassment should be set aside and questions asked.
or
One must discard all embarrassment when training in tea for this is the foundation of mastery.
or
One should abandon feelings of embarrassment and ask people questions; this is the keystone to become adept.

This poem can be interpreted in many ways, but to my thinking, I would like to put the emphasis on not being embarrassed rather than asking the questions.  In the previous poem, learning by looking and studying is emphasized, so before you ask questions, take time to look, study and reflect on what it is that you have a question about.

The matter of asking questions comes up quite often with my students.  In a lot of learning situations here, asking questions, having discussions and debates show the teacher that you are engaged and participating.  But as I wrote in this post, there are appropriate times and appropriate questions. And don't forget, the poem doesn't say ask your teacher, there are other students in class, and your sempai (senior students) who may have asked the question previously who may be willing to help you out.

As for feeling embarrassed, some people have no problem with this, others may feel embarrassed because they are beginners, or more junior than everyone else. This is the time to discard your embarrassment.  We were all beginners at one time. You are here on the path and everyone has his own journey in his own time.  Ask your sensei if you may ask a question, or if it is an appropriate time to ask a question.  Don't be embarrassed.