Write your logline. Use active voice and keep it brief. Don't name characters, but rather give a simple description of them if necessary. For example, "An aging rock star attempts to mount a comeback show, before he's visited by a former love with some surprising news."
Ask yourself if the logline is intriguing, if it gives a basic idea of what the story is about and if it is brief.
Practice reading your logline. Say it with conviction and force, but don't yell or go over the top. Practice until you sound confident when reading the logline.
Read your logline for the interested party. Again, sound confident, but not like you're trying to perform an intense dramatic reading.