You will likely want to look at 1st year retention separately from tenured retention. First year will always be lower.
You will also want to look at customer retention as well as wallet retention.
In terms of benchmarks, I would say that you want to be at the 80%+ mark for 1st year and 90%+ for tenured in order to have a successful SaaS model.
Best practices is likely a longer discussion: Some things to think about are a proactive customer contact strategy, doing some predictive modeling of churn and identifying those customers at highest risk, making sure that your onboarding program is solid.
Hope this helps. Happy to chat more.