In Superman's case, I don't even see the need for a secret identity, he's Superman!!
He should just say; "Hi the name's Clark, just provide me all my basic earthly needs and I'll save your asses every five minutes. And I don't work weekends."
That's the difference between the DC and Marvel Universe. For the most part Marvel's superheroes let everyone one know who they are. In the DC universe the secret identity seems much more important.
The older I get the harder it is for me to suspend disbelief that people don't know Clark Kent is Superman.