How to write a one man show
Research should be the start of any creative project. It informs, inspires and equips you in your endeavours. So before you put pen to paper, or fingers to keyboard, seek out projects and information which will help you to do a good job. Go to the theatre, watch standup comedy, hang out on youtube for a few hours and take note of aspects of the performances which appeal to you - the presentation, the writing, the characterisations. These will be fuel which can energise you in your quest.
When writing a one man show, it's best to have someone in mind for the part. An actor's talents may be limited or wide-ranging and your writing should be mindful of this. If his/her skills include convincing voice characterisations, musical ability or the ability to perform stunts, that may affect the character or characters that you develop in your script.
Have a theme. All good writing has a theme at its core. Your theme can be anything - don't take drugs, take drugs, put yourself first, live for others, don't live at all - only you can decide what your theme should be, but it should be evident throughout the work. The audience needs to understand what it is you're trying to say and without a theme, you will be in danger of losing them. Your theme will help you to keep your writing tight and to keep your audience engaged.
A one man show need not necessarily comprise a storyline - it may be abstract, musical, comical, dramatic or purely surreal. Whatever your approach is, be certain that you know what kind of audience you are playing to. Don't be broad in your approach - all good writing is by nature esoterical. You have to be certain that your audience will be receptive to your content and style and can relate to your theme.
As with any piece of writing. Begin with an outline. This will keep you focused during the writing process. Once you have completed your first draft, write another six or seven. Be brutal - make every word count. Be sure to give your show pace and variety. Don't dwindle in self-indulgent monologues or your audience will get bored.
Furthermore, be sure that your show is doable. You don't want to write something which is technically unachievable or is beyond your budget. A black backdrop with minimal props is far better than a poorly built set.
Finally, don't wait for inspiration to write. Just start writing - inspiration will come. 95% of what you write may be rubbish (this is the case for many successful writers), but the remaining 5% will be gold. The more rubbish you write, the more gold you acquire. Eventually you'll have something which resembles a finished piece. Once you have, don't be afraid to edit. Strip it back to only what's necessary. Don't say the same thing twice and don't miss out essential information. Keep it flowing and pacey.
Finally, don't give up. Perseverance pays off. All great writers will tell you that persistence is the key to creating good work. If you have the desire, you probably have the ability too.