From EffectiveLinkedInUpdates

Direct LinkedIn Updates

LinkedIn provides multiple ways to send messages to and update your contacts through your profile, jobs, updates, answers, forwarded member profiles, etc. Note that they're only practical if you have a few hundred or less connections. Otherwise you will need to invest a fair amount of time sending multiple batches of such updates. See ConnectionContactLimit.

Here are a few tips if you do use direct LinkedIn updates:

• Don't accept the default messages. People tune them out. It's your opportunity to be personal and to brand.
• The default profile update simply drives people back to your profile without any indication of what's new. You can't expect your connection to remember your entire profile. Tell them what's changed in the update message.
• Some messages like the profile update force people to click on a link and go back to the LinkedIn web site. That requires user intervention and forces him to wait as the browser is started and the LinkedIn page is loaded and displayed. It's totally unnecessary. Be respectful of your connections' time. Most members receive LinkedIn messages via email. Tell them in the email what's new. Don't force them to then go to the web page.
• In general make sure your news is highlighted in the subject so people open the email and the details are in the body of the email.
• If you're sending a job, note the location of the job in the subject