All but ONE of the following is a good rule of thumb to follow when delivering your speech:
a. memorize your speech so you don't forget anything.
b. use gestures to accentuate points.
c. maintain eye contact with your audience.
d. rehearse your presentation.

a. memorize your speech so you don't forget anything

Explanation:

In other to have a good presentation, there are general rule of thumb one must follow to impress the audience, amongst them are the following:

1. Rehearse your presentation very well before going to deliver your speech: this helps you to focus on the main message, without saying unnecessary words or going blank.

2. Maintain eye contact with the audience: by engaging your audience, it makes you appear confident and comfortable.

3. Using of appropriate gestures to accentuate point: by gesticulating appropriately, it helps to makes the audience understand your points more, and shows that you understand the speech your are presenting.

However, what one should not do, so as to be successful in presentation of speeches are, but not limited to the following:

1. Memorizing the whole speech: while it is good to rehearse and memorize some key points, it is a bad idea to memorize the whole speech, as it will affect your presentation. Not only will you appear robotic or naive, but there is every tendency to forget some keywords or point of the presentation.

2. Do not use big words: using big words or grammar might be tempting as to impress the audience, however, it may not be the entire audience that can understand those big grammar, so it is best to keep is simple.