It's also a bit tacky to have multiple siglines. Pick one, rotate it with others should you be working multiple projects. They should be routinely updated anyway to keep them fresh. A signature line can be used a lot like a classified Ad if you're trying to sell something. It could be used for quotations to share your point of view.
Signatures can point to another location on the web like a webpage for more information.
It can of course include your name, address and phone number, email address and so on. Check your Email programs HELP menu and look for signatures. You should be able to find some information there about how to set one up on your program. Email software normally allows the creation of one or more sig files. As well as temporarily turning them off should you wish to send a message without one for some reason.