1). Memorizing - this is absolutely the worst way to keep track of material. People are preoccupied with trying to remember the words to say and not the ideas behind the words (or with the audience). As a result, normal voice inflection disappears. With memorizing, mental blocks become inevitable. With memorizing it is not a matter of "will" you forget; it's a matter of WHEN!
2). Reading from complete text - Listening to someone read a speech or presentation is hated by most people. People say, "If that's all they were going to do is read their speech, I could have read it myself." I'm sure many of us have experienced this at least once while attending a conference or two. Below are some reasons why I believe people read poorly:
3). Using Notes - This is the most common way for remembering material. Using notes is better than reading since the speaker can have normal voice inflection and make more effective eye contact. If your notes are on the lectern, you probably won't move very far from them. If notes are in your hand, you probably won't gesture very much.
4).Using Visual Aids As Notes - Simple visual aids can effectively serve as headings and subheadings. Speak to the heading. Say what you want to say and move on. If you forget something, that's okay; the audience will never know unless you tell them.
Practice creating just a few meaningful headings to use and practice using only these headings as your "cues". This will take practice, but practicing using only these few words will force you to better internalize your speech.