Some people like to Hummm. Others have developed a few words that they repeat during the meditation experience.
Personally, I have developed an approach to meditation that I do all alone and never in groups. I do it in the early morning, when it is still dark and totally quiet.
Try listening to a few musical selections that I have linked together into a meditation playlist. This consists of selections by Beethoven, Robert Schumann, Franz Schubert, and Gustav Mahler.
Many of then pieces I have chosen are mostly slow movements from symphonies that are particular favorites of mine. Be patient, and work toward identifying selections that you find to be melodic, and that tend to move you to a quiet, comfortable, and restful space.