Written conversations can be made more interesting by using alternative words to said. In the previous example, Arthur and Ford were shouting at each other (over background noise):
"He said something about a King," shouted Arthur in return ...
There are, of course, many alternatives:
"I'm taking up swimming," announces Arnaud.
Try to use different verbs with speech: it makes what you write more interesting! Furthermore, speech can be broken up mid-sentence, before being continued:
"There's this road in Scotland," explained Andy, "the fastest ever built!"