I'd agree with don't do a sock. At least PM them with a journal you use, could even be the character you want to play.

Also another thing you may want to be careful on is suggesting any sort of ships or kinks unless you know this player ships it or is cool with the kink. I don't see an issue with approaching them to ask about maybe some gen threads to start off with though and then both of you can see how well you mesh together before jumping into shipping or smut.