The technique is best explained with an example. Below is the first line of President Obama's inauguration speech.
I stand here today, humbled by the task before us, grateful for the trust you have bestowed, mindful of the sacrifices borne by our ancestors. President Obama
Technique by Example
Step 1
Say the line out loud a few times, as if you're going to try and memorise it
Step 2
Write down the first letter of each word, together with the punctuation. This gives:
I s h t, h b t t b u, g f t t y h b, m o t s b b o a.
Step 3
Repeat the sentence just by looking at the letters. At first you'll have to keep glancing at the complete sentence to remind yourself of the words, but it won't take long before you can just look at the letters. This is you beginning to memorise the speech.
Applying the technique to your presentation scripts
Write the letters and punctuation in the margin of your script. If you do that, provided you've spent time trying to memorise the script, you will find that during your presentation, a quick glance at the letters may be all you need to remind you of what to say. This will help to encourage a more fluid presentation.