Before developing a new Web Part, check the following
a. Is it already provided Out of the Box?
b. Whether a Data View Web Part can be used
It is recommended to develop the solution in the developer interface, and then migrate the solution to the development server. After thorough testing, the same should be migrated to staging and then Production
Check out the page and do your modifications
If editing an existing page:
a. Create a Copy
b. Make your Alterations to your Copyc. Make your Copy active