Are you anticipating it and doing something different before she lunges (ie: Keeping the leash tight)?

My Kaedyn lunges at people. I think it's fear related. If he was off leash, he wouldn't lunge but on leash, he's a naughty boy. He tends to lunge at large intimidating people (mostly men). It's too early to say if it's working but what I've recently started doing is taking treats with us during walks. I'd make him sit/down/come often. He pays much more attention to me during walks this way. He also gets rewarded for passing (and ignoring) any person. I want him to think of people as an opportunity to be rewarded, not corrected (what I stupidly did before). I'm not sure what else to suggest though.. a trainer/behaviorist would be a wise investment.