I assume we are talking about zonal geraniums? Usually, once the flowers are spent, the entire flower stem will snap off easily. This is not just the cluster of flowers at the top of the stem but the entire stem......it is attached to one of the major branches of the plant. Remove it gently - it should just snap off - where it originates fron the larger branch. Older yellowed leaves can be removed the same way to keep the plant looking neat and tidy.

Ok, so follow the thick stem that each bunch of blooms is attached down to the main branch of the plant and snap that off? Might help if I learned the proper terms for plant anatomy!