I would say, signature campaigns can bring some profit.
But if you do have a blog and have a talant to write good posts
Content creation is the best way
I would agree with Avalonist. By far the easiest is a signature campaign since it's a set and forget. You would only have to do your normal Bitcointalk activity and get paid. Developing content would pay the most, but normally you would have to be one of the first to get in on it, and it would talk more time to develop the content.
but most of the signature campaigns expect to do at least 4 posts regarding the bounty coin on given section of the forum. So that's bit difficult task, there is a chance to get your account ban if you violate the forum rules.