I think I have commented before how bird watching would often be better described as bird listening. The other bit of advice to accompany that would be stop and listen. Jane and I went for a walk this afternoon in the nearby Brasenose woods and it was notable how little birdsong there was even walking on a relatively minor track. Then we stopped and waited and, within a minute, the bird calls started up.
We still didn’t see much (a couple of blue tits and some kind of juvenile we couldn’t easily identify) but we certainly heard a lot more by taking a break.