I've about 40 databases with similar schema. So what can I to ensure these databases run easily?

Must I be optimizing tables regularly? How do i identify table crashes?

As referred to at length inside the below article, the minimum actions you need to perform include,

  1. database backup
  2. check table integrity for errors
  3. optimize tables (varies between MyISAM and InnoDB)
  4. evaluate

http://www.laurencegellert.com/2011/07/mysql-maintenance-tasks-for-innodb-with-mysql-5-1/