I'm not sure how I'm supposed to do this but let's try this:

I'm having trouble writing Arthur. I'm trying to figure out how he acts when he's scared/nervous. Any help?

Quote Originally Posted by butter_beer_drinker
If his kids were around I am sure he would try not to show it. I have seen a few people write him as a dimwitted, Muggle artifact-loving, freak, but I don’t think that is right.

All dads fear something, the number one thing being someone harming their family. Since the Weasley’s are a large family, I’m sure Author would be very fierce when defending his family and would later break down in the arms of his wife. He would try very hard to not let his kids see his fear. If they were around it would probably manifest itself as anger. He might be harsh with his kids when telling them to do something and would later apologize and tell them he was frightened for their safety, or something along those lines.

As for being nervous, he strikes me as the type that would become somewhat chatty. He might try to strike up a conversation about anything in order to hide his nerves.
Quote Originally Posted by kathryn_malfoy
I have gotten the feeling that Arthur tries to stay very calm, no matter what. I think in a situation in which he was afraid, he would try to laugh it off and rationalize. He does not seem like a rash character at all.
Quote Originally Posted by TiaBlue
In my opinion, Arthur Weasley seems like a person who overcomes his fears and calmly does the job that needs to be done. In Book 4, when the Death Eaters were terrorizing everyone at the campsite of the World Cup, Arthur was calm in the face of danger and ready to fight. (page 120) Also, he was calm and determined at the Battle of Hogwarts in Book 7, and other people must have seen duelling skills and leadership in him because he was put in charge of taking groups onto the grounds to fight. (page 611)
However, Arthur wasn't calm when he was afraid George was hurt in Book 7 - he was kind of fierce. Remember how he yelled at Kingsley even though Kingsley probably had a wand pointed at him?
page 74 American edition - "I'll prove who I am, Kingsley, after I've seen my son, now back off if you know what's good for you!"
Harry had never heard Mr. Weasley shout like that before.
The only time I can recall Arthur getting nervous is when he is trying to avoid confrontation with Molly. He has a healthy respect for her wrath! But remember, it was Molly who was falling apart after the World Cup incident and Arthur who was soothing her in Book 4. (page 146)