Freebie for newsletter subscription on salespage

[aricia]

Hi I would like to steal your minds on something!

I'm doing PPC and other methods to get people to my sales site but the conversions are not great.
I know listbuilding is a good thing to try to sell the product or similar product later on.

My questions is, should I offer a freebie on the salespage for inscription on a newsletter or should I put this rather on a blog kind of site?

What do you think?