Thanking Sensei

Get up and go to Sensei. Use Shiko (knee walking), unless Sensei is very far away or has walked off the mat. If you don't yet know how to do Shiko, it is perfectly fine to walk normally. Sit in a semicircle facing Sensei and, when it is your turn, bow and thank him. Sensei will, of course, bow and thank you for coming to practice Aikido that day.