A CEO of a well established food company once recommended me a book about designing a challenger brand. As someone who knew very little about branding and positioning, I found one particular exercise in the book really powerful.
I've tried to explain the diagram (and exercise) as best I can here. If you find the whole 'branding thing' a bit useless, this little diagram might be a good shortcut for you, and change your mind. Especially given we are all just trying to make it work without access to big marketing budgets.
This is also an activity you can do for free. And I like free.
https://medium.com/@jesterhoax/branding-a-startup-18f65e96e4c4