I recently started using the LinkedIN plugin for Outlook. At first I just enjoyed having profile pictures load, it’s an easier way to identify with whoever you’re communicating with. Then I noticed how much easier the social plugin had made it for me to connect with my contacts! Within a few weeks the number of contacts I had n LinkedIn had gone bonkers. Not random people, real people that I knew. It’s surprising how many people you actually communicate with, and it’s far better to connect to them on LinkedIN than random people.
There’s a social plugin tool for gmail / google hosted domains too. Whatever your email solution is, a LinkedIn social plugin is a must. It’s the easiest way I’ve found of keeping on top of connecting with my contacts on LinkedIn.