Scripting has its place in webinars and webcasts. Moderators should usually have initial technical instructions and speaker introductions scripted out. Presenters often benefit from scripting their opening and closing paragraphs to help them move smoothly into and out of their presentation flow. And webcasts created purely as short, focused recordings should always be scripted.
If you write out something for use in your presentation, it is vital that you read it out loud as you are writing it and as you practice your presentation. Some things look good on paper but sound terrible when they are spoken.
A writer can get away with a phrase like: “The mellifluous chant of the muezzin wafted sonorously over the languid sun-baked square.” But words such as mellifluous and muezzin can trip up the best of speakers, and all those sibilant sounds at the end of the sentence are going to make you sound like a snake. The sentence is also likely to come across as rather flowery for conversational speech.
In general, your script should favor words of fewer syllables and short, powerful phrases rather than long sentences filled with adjectival elaboration. When I write scripts, I say each sentence as I type it. If I stop to think about what I want to say next (yes, it happens) I start by saying the last line I wrote to make sure I keep the tone and flow consistent.
If you want a practical illustration of this tip, attend a public webinar featuring a guest speaker. Almost certainly, the host will have a short biographical introduction for the speaker. Almost certainly, it will have been lifted from a web page or formal professional document. Almost certainly, the host will read it in a singsong recitation that sounds nothing like a human being talking to you. It’s a great way to hear what not to do.
You have a lot of experience listening to people and determining whether they sound natural and convincing. Use that on yourself. Read your material out loud and trust your ears.