This is one thing which is a rarity. Most of us are scared of standing up and making a presentation. Finally when we stand and talk, we don’t even know what all went wrong and what went right. We have an overall feel, but that is too generic. General feedback like “you did a bad job” or “you were great” makes no sense. You need to know specifically what you did well which the audience liked and where you need to improve. “You chart was well made but you were not looking at us” is a better feedback to get.
When to ask and who to ask is very subjective. You cannot ask your client how your presentation was. But if she says, “I liked how you presented” then you can always pounce on the opportunity and seek some specific feedback from the client. At the office, you can always ask your colleagues to tell you after every presentation what went wrong and what was great.
Once you have your regular feedback mechanism going, go to every presentation with 2 or 3 clear objectives. “I will try to put less text on the slide and keep the charts simple and will not lose eye contact with the audience.”
If you are reading this then I guess you are already serious about your presentations which takes care of 20% of your work (1 element out of the 5). It is now the 4 other areas where you need to work to become an accomplished presenter.