RAK means "Random Act of Kindness". In the genealogy world, this means doing something nice and genealogy related for someone else for free. With the prevalence of social media and family history websites, this is easier than ever.
You can easily join an online genealogy group (on facebook for example) for the regional area you are researching. You can also join one for your own local area. The purpose of joining a local area, as opposed to where you are researching, is to help be a researcher for others. Someone might have a question that, as a local, you can easily answer, or go look up in your library. And this good karma comes back to you, because later when you need information from far away, there will be a local there to help you out too.
So, don't forget to 'pay it forward' and do some random acts of genealogy kindness, and do local lookups for others.