Mistakes Designers Make in Presentations

1. Don't be the clients friend. You're there to solve their problem, don't try to please them/make them happy. Help them meet their goals! Don't avoid confrontation.
2. Don't be lazy in the presentation and take charge of the situation. Confidence is about making the client feel better, securing their trust. 
3. Don't start with an apology - this will cause them to distrust you.  The best way to fix a meeting is to cancel it and then rebuild the work until you can present it confidently.
4. Set the stage properly. Let the audience know why they're a part of this conversation, thank them for their time, make them feel like experts. Tell them how long they'll have to be there - 'we're looking for client approval today' and they'll be looking towards the goal of the meeting's end.
5. Don't patronise/bore the client by 'over explaining' the design. Sell benefits of the work, the money it will make them, how it will compete with competitors. Make the client relate the work to their own lives and tell the story. 'Present like a snake-charmer'. 
6. Don't take notes until afterwards.
7. Don't read from a script - you are making a performance. It's the excitement that sells the product.
8. Don't get defensive. 'I am not my work', the work is not a personal expression - the client is free to criticise it. Good people do bad work sometimes!! When you're getting feedback keep your mouth shut.
9. Don't mention typefaces - they don't give a shit about that. They don't know anything about this and don't want to be made uncomfortable. 
10. Don't talk about how hard you worked, it's not like you're getting graded on effort. Don't show them the process of getting to the end result.
11. Don't react to questions as change requests. 'Why is the logo small?' - 'I can make it bigger!!' Sometimes the client just wants reasoning.
12. Always guide the feedback - tell the client what kind of feedback you want/need. 'How well does this reflect your brand, your users' needs and your ad strategy?'
13. Never ask - 'do you like it?' Far too subjective, it disregards all the reasoning and logic behind the design. Don't seek the safety of being told your design is liked, your design need to solve a problem. What they really want it success. 'Work you did not sell is no better than work you did not do.'