One effective way I’ve found is to piggy back on trending news items and creating a blog post and action around it.
Here is how we did it for one of my clients.
When almost 300 Nigerian girls were kidnapped in early March for attending school, the hash tag #bringbackourgirls was trending worldwide.
My client – a coalition of charities working in Africa — used this opportunity to write a blog post about one of its member charities and its efforts to get people to act against a similarly evil group – The Lord’s Resistance Army. We created an action item which we linked to through the post asking people to stand with girls pursuing their education so that we could grab their contact info.
My client also has a relationship with Care2, so we were able to re-publish the post on their website providing even greater exposure. Many Care2 readers tweeted about the post and by doing a Twitter search we were able to identify who they were and ask them to take action as well if they hadn’t already done so.
Finally, we used our Google Grants (Adwords) account to direct people to the action for search terms like “Nigerian girls” and “#bringbackourgirls”.
We have acquired over 250 emails so far in a little over three weeks and every day we’re getting more. Cost per lead: $0. That’s a pretty good return on investment.