"It was important for those communities to tell us what made a good night out," said Mr Harris, whose recent work includes Cardboard Dad at the Sherman Theatre and The Gold Farmer for BBC Radio Three.
"It was interesting how many people told us about nights that went wrong! I collected a lot of inspiration from the stories I heard, about the characters and the buildings themselves."
Six short pilot scenes were then performed to the communities for feedback.
"People love to see good acting," said Mr Harris. "They liked the mix of the comedic and dramatic elements, which I think sums up the valleys!"
A Good Night Out's six-strong cast, including Boyd Clack and Siwan Morris, are all originally from the valleys.
Mr Harris is modest about writing NTW's first production but describes NTW as "vitally important".
"As a nation it's vital that we have our own identity and the national theatre is an important part of that," he said.
"It fits into the sense of a nation starting to realise its cultural potential.
"We have had the assembly government for a number of years and that's starting to bed in, so I think this play came at an interesting time.
"Wales is changing and so are the valleys.
"You can't ignore the past but you can't live in it. It is one of the big themes that people brought up again and again in different communities."
One of the characters in A Good Night Out was partly inspired by 81-year-old Bill Thomas, the voluntary manager and licensee at Bedwas Workingmen's Institute.
"When we were boys we used to come here dancing," said Mr Thomas.
"We used to be here twice a week for dancing, billiards and snooker.
"The hall has seen so many different people here. In the distant past [American concert singer] Paul Robeson was here and it is reputed that [soprano] Maria Callas sang here, but I don't know."
NTW was launched in November last year to showcase Welsh writing and performing. It was founded by the Arts Council of Wales and is funded by the Welsh Assembly Government.
Other shows to be staged by NTW in its first year include the premiere of a John Osborne play, "reality theatre" staging events outdoors, and an interactive event on the beaches of north Wales for the "Play Station generation".
Actor Michael Sheen will also return to his home town of Port Talbot with poet Owen Sheers to stage an contemporary revival of the town's community Passion Play.
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