They usually leave the pond after breeding, but of there is alot of aquatic food they may stay longer.
When they are hunting in the pond they will dangle motionless stalking prey.
If they hear or see you or a predator they will quickly disappear.
Newts are largely nocturnal, especially when they are out of the pond. Try going out with a torch and looking into the pond, and also looking around the grass and planting beds. Watch out you don't tread on any!