Some ideas for taking the register:

01 Spell name / surname
02 Spell name / surname in reverse
03 The class say their first names in alphabetical order.
04 The class say their names in reverse alphabetical order. 
Both 03 and 04, at first, require the students to talk to each other and work out the order.
05 Each student says an animal that starts with the first letter of their first name. if a student gets stuck the class help.
06 Other things that could be done with the first letter of their names in the following classes: countries, adjectives, verbs, places, sports, professions.
Eventually they will have a list of words starting with the same letter which could be written as an alliterative sentence.
e.g. Paula from Poland will be a perfect police officer and play pool in the post office.