When should I select the Accepted Solution button?
Answer: When another user post a response that fixes your hardware or software issue. 
What if a better solution presents itself?
Answer: The original poster may change the Accepted Solution or the original poster can ask a Dell Community Liaison to make the change. 
Who else is authorized to change the Accepted Solution?
Answer: The Original Poster or a Dell Community Liaison. 
What should I do if I accidentally select the wrong solution?
Answer: Go to Options and at the bottom, click Unmark Accepted Solution then choose the correct one. 
Why did the Accepted Solution I selected change?
Answer: After review a Dell Community Liaison thought another solution in the thread was better.
How will Dell use the Accepted Solution results?
Answer: The Accepted Solution results will be gathered and fed to other support tools.
Can I select my own post as an Accepted Solution?
Answer: Yes, but only if it is the answer to your hardware or software issue. If you are thanking someone, do not mark that as the Accepted Solution mark the instructions they gave you that fixed your problem.