Ask good questions after putting effort into finding the answer first.
Answer questions with just the right amount of detail. Be respectful, polite, and reasonable.
Upvote good questions that show some thought; likewise for answers.
Downvote only if the answer is improper or incorrect.
IOW try to make SO enjoyable for all (and so enjoyable for me!)

What I use most: Linux (Ubuntu); Python 3.x (and 2.x); C. Also have done Android/Java; Windows, C#; iOS/iPhone/Objective-C.