Linked In Tips

I had not really had any idea how many different tips and conversation there was surrounding how to do a Linked In profile. I have gotten emails in the past from peers asking to add me on Linked In, but I have never had any experience with it outside of that. From the lists of tips and tricks and from what we have talked about in class it does seem like a tool that could be extremely useful when trying to find a job.
One thing that all the lists had in common was the emphasis on how important your photo is on Linked In. At first it might seem surprising that it is so important, but really when it comes down to it, it would likely be as important as making sure that you look professional when you show up to a job interview. What you look like probably should not be a factor in whether or not you get hired, but making a good first impression is definitely vital when you are networking.
I would be curious to find out more about the groups that some of the articles mentioned. What kinds of groups are available to join? What would being active in the different groups entail. Some of the articles mentioned being an active member of two or three of them, and I am not sure what exactly that would mean. They also mentioned that having your Twitter handle in your Linked In profile. Is that really something that potential employers and contacts are interested in seeing? How important is it that I cater my different social media accounts to appeal to an employer?