First of all, you'll want to get a picture of the health of your email deliverability. Given that nearly everyone's using Gmail these days, checking your reputation with Google will give you a great overview of your sending reputation in general. Set up Google's Postmaster tool
to monitor performance of your email. If you're having issues on Google, you can be sure you'll start to see issues elsewhere soon enough. This tool can help you to get ahead of problems before they ruin your sending reputation.
If you're an InTarget customer, you can see all the statistics of your campaigns in our Marketing Module: