
This is one of the reasons why collaboration (read: goofing off with colleagues) is so important. Write down all the clever you can. Go nuts and go a little too far with it. Share your cleverness with anyone and everyone who will listen (but be careful not to bore your co-workers with your own genius, please).
Then put clever to bed. Get a fresh page and write down the driest, most boring headlines you can come up with. State the obvious. This isn't an opportunity talk down to the audience, even in jest; rather, just say it like it is. Selling crackers? Write "Buy our crackers."

In the morning, with a fresh cup of coffee, look at both pages side by side. Clever will have lost its tug, and you can now see some of the gems buried within even the most asinine of headline spoofs. Bring these over to the matter-of-fact language that describes where you need to go, and you may find yourself with something truly valuable.