First of all, you have to develop an idea for your application. It is extremely important for you to ensure that your application suits the portable devices. Furthermore, if you want to market your USB application, you must conduct a thorough market analysis so as to assess its demand and the level of competition in the existing applications.
You will have to analyse your application in a profound manner in order to make it portable. See whether the settings are saved or not. Besides, you must ensure that your application has all possible command line parameters.
It is extremely important for you to keep your application light. You must only keep the useful features of the application. Moreover, you have to decide whether your application code will be proprietary or open source.
Now, start writing the code of your application. You can seek different codes for USB application on the internet. However, only copy those codes which are free to use i.e. open source codes. After that, programme the main features of your application; developing its launcher and installer.
If you want to copyright your software, you will have to license it. If you want to keep your software open source however, you will not require any kind of license.
After completing the programming, you have to compress your USB application. Although, the compression doesn’t help reduce the size of the file, but it boosts up the launch speed.
Now, you can host your portable USB application for public. It will be better for you to test run your application with a beta tester developer forum or with any open source development website.