Talk about a new challenge! While I'm trying to teach Alfie what I'd like him to do (follow a specific scent trail, to the exclusion of all other distractions), he has something to teach me too: how to read his body language. Although there are whole books written on that subject, the key thing seems to be that all dogs are different, and you have to learn to read your dog. So I've been trying to consciously take note of all the little signals Alfie sends while working.
In general he looks focused and intent while on a trail -- loose tail, nose twitching, ears and eyes moving, mouth open. Normally, when we're just out for a walk, he's easily distracted by every admiring passerby -- not when we're on a scent! He ignores them like they don't exist. Once a man tried to pet him in harness and Alfie just gave him a half-wag and an apologetic look like, "Hey, sorry, I'm kinda busy right now!" So funny, given Alfie's usual life-of-the-party personality!
He always seems to know the general direction to take right off, but depending on terrain and wind, he'll then start to "cast" in loose s-curves right and left to help narrow down an exact route. The interesting thing is that while doing that, he'll start glancing in the direction he favors, even while casting right and left of it. That glance is really key for me to notice because it usually seems to be correct -- he knows that's the way he needs to go, but is just making sure and narrowing it down.
When he starts getting close to the subject of our search, he doesn't look (to my eye at least!) more "excited"; but he does gain a ton of confidence, moving much faster and leaning -- hard -- into the harness! When he "finds" successfully he dashes right back to me for a yummy treat. I have a feeling that once we start finding actual DOGS he'll be so focused on them that the treat will become superfluous!