If you sight a couple of tour buses in the car park, it's safe to assume that if you want to talk to someone about the wines you're sampling you'll probably be better off somewhere else.
Second, I like to see a tasting area with room for more than two or three groups.
If the place is handkerchief-sized and there's a tour bus on the premises, it's going to be a waste of time. Even where the tour buses don't run, it's nice to have room to taste without rubbing elbows with total strangers.
It also helps to be able to avoid overhearing what they're being told as they sample something a bit further down the range. You're going to hear that eventually, but these things are best happening in their own good time.
Third, and most importantly, if you're a winery that's serious about your cellar door operation, you need cellar door staff who know their stuff. Hopefully, they'll go about the business of quietly selling both your own product and your region as a whole.
We'd seen both extremes in the Swan Valley.
At Sandalford, the girls in the room dispensed the tasting samples with alacrity. Then they left you to it.
In contrast, the dude at Houghtons engaged in a dialogue and ended up selling Hughesy half a dozen $50 reds (substantially discounted, but still at a price point where I'd usually be looking elsewhere).