Before making your own project, explore the site
a bit to understand how the projects work - take a look at a few projects (but don't feel intimidated, even simple projects are worthwhile!).
What can you show in your project? How to make something, how to do something, how to fix something, something you started but want help with.
Commercial posts: As long as your project focuses on instruction, assembly, use, repair or hacking of your product you are welcome to post (the full Terms of Service still apply).