That is how you end up never contributing anything or having your first pull request be rejected.

Best way to avoid having your pull request rejected, is to make sure the change is actually wanted, which you can figure out by communicating.

So if some random webapp has a button in the wrong place, don't open a PR moving the button to the right place, open a issue and confirm it's wrong, and confirm the maintainer(s) would be fine with the suggested change. If something is unclear, clear it up before spending time on the PR.

Once consensus is reached, it'll be trivial to get the PR merged.