what are the checks that we can run on daily basis such as status of the aggregate, volume , luns, disk, disk shelf, delayed write or read operation, load analysis etc. which can be included as a part of health check or proactive monitoring?
A good start is to install OnCommand Unified Manager Core (also was called Data Fabric Manager (DFM) or Operations Manager) which does monitoring, reporting and alerts. It also has a plugin called the NetApp Management Console (NMC) which uses the DFM database and has Performance Advisor which can be used to look at proactive monitoring and alerting. It should get most of what you want for health and practive monitoring and it is free (request a key if there isn't one in your entitlements).