LinkedIn is the known the “professional social network.” In many ways, it's not even a social network - it's more like a professional network where you won't see many people younger than their early 20's. The type of information you should share and read will be focused on industry or market that it is targeting (no cat pictures!).
LinkedIn allows you to connect with other professionals in the strength & conditioning and make a professional appearance online. That allows you to stay in touch passively by just being a member of the network. However, perhaps the best part of LinkedIn is the job opportunities - the professional network is growing rapidly mostly on the fact that it is the world's most powerful matchmaker.
You should update your profile about anything that happens in your career. Think of LinkedIn as your online record of your advancement as a professional. Be sure to proofread everything you write, even if it’s a simple comment in a group discussion.
Speaking of groups, make sure to join them! They are insanely valuable as many S&C professionals from all over the globe contribute and discuss topics, articles, and debate on different issues in these groups. We've pulled what we think are the top 5 groups to join on LinkedIn for strength coaches: