Any other content you can make, such as stuff on YouTube (as mentioned before) also work quite well.
Don't do sig campaigns unless you truly believe in the product that you are pimping.
EDIT: I am not being 'Holy than thou' either. Been there and done that and felt like I needed to take a shower after looking at the shit show that the link led to.
I don't current have any major coding experience, and I don't have a lot of advanced software related to Internet freelancing, so right now I'm using the signature as a way to earn some Bitcoin while I'm getting more practical experience.