In public school these days I just go with Korean names, but in my hagwon time I used to let the students pick their own English name. Write the alphabet on the board and have the student pick their favorite letter. Then write out three options of that given letter -- Jeremey, Josh, Justin -- and have the student pick their preferred name. Cross out that letter and let the next student choose. Each student having a unique lettered name makes it even easier to memorize them all!