Pronunciation:Words should be pronounced clearly, with proper stress and intonation. Mispronunciation sometimes leads to confusion and spoils all presentation howsoever well planned it is.
There are about five requisites of effective speaking- articulation- how well we voice the vowels and consonants while uttering words and sentences, the accuracy that accounts for quality or state of being precise or correct in presenting one's views as well as pronouncing words. The third requisite of effective speaking is tone. The tone is used to convey how the speaker is feeling about the viewpoint or opinion they are expressing.
For example, you can use a happy tone to outline his/her delight while a sad tone highlights their disappointment in the concerned issue. Apart from articulation, accuracy, tone, pitch, the highness or lowness of voice also differentiates good and bad speakers. You should modulate one's pitch according to the situation in which one is speaking. Last but not least is a projection that is how you project your voice while speaking. Rather than speaking too loud or slow, you should speak in a moderate way taking into account your listeners requirements and level of understanding.
Communication is a two-way activity, so always take into account your listeners feedback and try to amalgamate that in your speech.