Spaying a cocker spaniel- when is the best time?

[SunshineDaisiesButterMellow]

Pup is only 4 months old at the minute but I was just wondering when was the best time for them to be spayed? We definitely do not want to breed from her. I have heard different things from different people so thought I'd ask on here.
Some friends were saying to wait for her first season. When will that be btw?
And some were saying between one and two years old.

Any advice and what should we expect when she is done?

The most important thing is to get it done before the third season to gain the protection against mammary cancer.
After that it is all down to personal choice extensive studies have found no benefit to either before or after the first season.