i would say your best chance of seeing one is between april and august as activity outside the set before dark is high - either young exploring the world or foraging before dark. i saw one late last year at about six in the evening plain a day just wondering around some field margins, so that was very lucky.
but if your going to watch a set follow some basic stalking rules dull plain clothing, quiet as a mouse, very still, down wind of the animals, etc.
someone also told sit above the set, even with a torch it dosnt spook then as much as they expect light form above.
good luck anyway
