How to contribute best?

[Lejo]

I lately saw and also wrote to multiple topics about how to improve the review process of PRs or what the core devs can do better:
viewtopic.php?t=25507
viewtopic.php?t=25514
viewtopic.php?t=25417

But what if the core devs do everything right and just the contributors create the problems?
So what can we as contributors do better? I hope we can make a great list how to contribute in the attitude of the core devs.

There are already the CONTRIBUTION Guidelines but I'm sure we can find more.

So let me begin:

• Always double check if there is already a topic for the own problem to prevent duplicates
• Fully test your PRs
• Correct errors (checks) independent
• Add needed documentation
• Use short and clear messages to explain your problem
• Answer quickly to requests/qustions

Now it's your turn!