Developing as a presenter

Trust yourself
If you do not think you are up to a particular presentation either get help (do training courses and rehearsals), or get someone else to do it (there's no shame in recognising your limits). However, most people have better presentation skills that they think they do. Recognise what you have. If you doubt your ability to think on your feet, for example, then defer questions till after the presentation. Similarly, do not use a joke as an ice breaker if you are not good at telling them.
Success is the best presentation.Don't over reach yourself. Several short presentations that you feel went well will do you far more good than one big one that makes you sick with nerves and leaves you feeling inadequate.
Feedback
Encourage those around you to tell you the things you did well. Very few of us make progress by being told what was wrong with our presentation. When we're up in front of an audience we all have very fragile egos.