Tips for retaining members?

Coming from an SaaS perspective, I'm interested in learning more about membership engagement and retention. While I've found it relatively easy to come across methods for engagement, I've found it harder to find methods for retention. Outside of asking your membership questions about why they are leaving or why the are dissatisfied, or offering new products or discounts, what else can I be doing to get my members to stay put? What are some retention tactics I can put to use?