That how I'd pronounce it while all the Japs rolled their eyes or looked confused.
"Sho-Sen"
instead of
"o-kawa"
Yep. That's how good my kanji is. I'm even struggling with the kana it's been so long. 
How the hell do you know which pronunciation for a symbol to use? I asked a guy that once and he said: Be Japanese.
Guy's name is Ogawa, mostly names are kunyomi, but not all. onyomi surnames are rather seldom, depends a litlle on the time they were established. otherwise, it all comes down to experience and a little guessing. The more you read and talk to japanese, the safer your guessing gets.
the guy's name is Norihide i think, but there are other possibilities too. Ogawa is safe though.
