Facebook, twitter and many other social networking services are great because you can do a lot of different things on them. Still, if the point is to build up your list, you have to remember to make it interesting, especially towards the target audience.
On Facebook you have to join groups within your niche. It’s a great way to promote your product. Very important is that you don’t only pitch. Give aways are in place here. In this you have a very targeted audience.
On Twitter you deal with micro format, witch is actually pretty useful. In fact, if you do it right, you can use this to get some real time leverage for your business.
You can use the framework to drive people to your squeeze page, or use it to make announcements of new blog posts. Of course, at its core you can use it to meet new people who are interested in the goods or services that you can offer.