Concerning the signature set-up there is a great video on youtube, explaining very nicely, how to select the right signature and how to find the Bitcointalk ID and how it needs to be added in the signature. I just also followed it, to make sure I have updated the signature correctly as my Bitcointalk level just changed. So do not forget to keep your signature updated when you change your Bitcointalk Level!
A Youtube video is excellent. Many people won't watch it, however. It should not be required to watch an external video to understand how to sign-up - the process should be 100% clear from the sign-up process itself. Otherwise, we are guaranteed to lose a large number of sign-ups.