Following Points according to me:
Attend sprint-Planning sessions
Attend Daily Stand up
Dont save all the testing for the end; test throughout the sprint
Meet with the developers for bug fixes and if he /she dont fixes then talk to directly Product Owner or Test Manager
Attend Sprint retrospective
Document Test cases and if bugs found in production when release deploy then take RCA Urgent and hot fix release go live.
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Agile point of view::
Understand user stories and acceptance criteria
User stories get clarified from the respective stakeholders where there is insufficient information
High level test strategy has to be decided for whole release
All the risk that might occurs at the time of release needs to be noted or documented
Number of testing types need to be decided and discussed
Estimate time for each user story test case creation and execution
Break user stories into different testing tasks
Decide each story test coverage
Acceptance criteria for user stories needs to be defined
Understand and plan for user stories automation and support various levels of testing