I like to keep mine as simple as possible, but I've seen some very elaborate ones - ones with stars in! Please share your tips about writing a good forum signature here
A phrase that is different does it. Something that gets people thinking. I'm sure if you had something in your signature saying PR - 12 and then the link, people would check it out.
I think offering people something would be a good idea also. for example, "free backlink" or maybe something to suggest urgency - like "for a limited time only"
It depends, if you are talking about the signature on your own site, you should include links to interesting threads ... If you are talking about other sites, use the signature for links to your sites ... Check out my signature for example
Signatures are something that enable us to share something with other members in forum. A good one make our image better. This's like win win situation.