I don't think it's necessary for everyone to have history with everyone else, but are my ideas for Valdred (going off the information everyone has provided):
Valdred and Aliss: With Valdred's family history he's not the most vigilant lawman around, so he probably let Aliss and her brother off with a warning when they poached the deer. It was still a bit risky to do that, so he may feel that Aliss owes him one.
Valdred and Dougan: Cross the Harkenwold enough and you're bound to run into Valdred; the same sounds true of Dougan. They've probably seen each other in odd places from time to time, but Valdred isn't the sort to strike up a conversation with a stranger. Valdred may have broken up a brawl at crossbow-point, but only if it was really getting out of hand.
Valdred and Munir: I like the idea of Munir and Valdred having fought for Tor's Hold, and later teaming up at Hammerfast. Valdred knows Munir's worth in battle and is glad to have him as a friend.
Valdred and Rivenalis: It doesn't sound like they normally run in the same circles, and Valdred tends to stay away from overt displays of religion. Hammerfast may be the first place they met.