The 1st thing you must recognize and accept in practicing your presentation is that reading your script over in your mind or thinking about what you will be saying is not a practice or a rehearsal. Just like athletes must practice and musicians must rehearse, you must work on your material out loud. Anything else is a waste of time.
For many people, the idea of actually saying their script out loud is something which they are reluctant to do. I can’t tell you how many of my clients and students come unprepared for their presentation, explaining that they read it over to themselves. Again, reading it over to yourself or saying it over in your mind is not practice. You must stand and treat your rehearsal just as if you were in a live venue.
The real question deals with how to handle 10, 20 or even 40 minutes of material? My advice is to break your presentation into block of information. Good public speaking courses will teach you to outline your material in the creation of your presentation; and, outlines are an excellent means of arranging your thoughts. But for means of practicing this material, you may find it easiest to look at your outline as blocks of information.
Your opening is obviously one block as is your closing; but, if you break your development down into blocks and learn each block of information independently from the others, you will discover a very effective means of identifying the purpose of each block with ideas, phrases, anecdotes and statements. In essence, each major point is a block.
For lengthy presentations, breaking your major points or blocks of information into sub-points or sub-blocks would be very beneficial; i.e. one major block of information may contain 2 or more sub-blocks. Learn each sub-block and then put them together into the main block. Rehearse each block or sub-block separately just like a professional musician would. If, during your practice, you have more difficulty with one block or sub-block, work specifically on the problem area until you know it. Practicing the entire presentation over and over is not going to fix the problem in one area. Go over the problem until you know it and then move on.
Recently, one of my newsletter subscribers told me that he had taken my advice: he practiced his 45-minute presentation in blocks and could not get over the difference it had made in his delivery. He was more confident and felt he knew his material better than he had in prior experiences.
By treating your presentation as blocks of information and practicing it in that manner, you will discover a much more effective means of truly knowing what you plan to say. And, the assurance in that knowledge is a marvelous benefit.