Plan out exactly what you want for the web app on paper, and be as precise and consistent as possible.

Then pick a language and set up a development environment. (A difficult step to get past, but you might be able to get someone to help you do this for free)

Then start reading tutorials and doing practice examples.

Once you have a feel for how to get a basic app up and running, go back to the specs you wrote earlier and identify some subset that you want to implement.

Begin implementing your idea until you get stuck. When you get stuck, research the language tools you need to get unstuck. If you find yourself hopelessly lost, either pick a different subset of your app to work on, or go back to reading textbooks, tutorials, and forums until you better understand the concepts.

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