Whether you're someone who has just started using LinkedIn or who has been using it for a while, I suggest you check out these LinkedIn Tips. These tips walk you through a step-by-step process of getting started with configuring your account and inviting connections. For those who are new to LinkedIn, I suggest following the steps in the order given. For experienced LinkedIn users, I suggest skimming through each step to see if there any steps you may have missed.
When I first joined LinkedIn, I found the site to be a little overwhelming. There are so many features it can be difficult to figure out where to start exploring. After spending a weekend bouncing around the site in an inefficient manner, I wrote the tips to help others get up to speed in a systematic and efficient manner. With every invitation to connect I send, I include a link to the LinkedIn Tips.
There are a number of other sites with LinkedIn tips, but I think these tips are the only ones which walk you through the process of getting started from scratch.