• Study and understanding the software requirement specification document
• Go through all the designs to understand the design requirement of software
• Prepare a test plan
• Prepare the test cases to verify each functionality
• Do testing with each test case and report issue if any
• Retesting of software after bug/issue fixed
• Give suggestion to improve the quality of software
• Communicate with the other teams like design team, developer team and the managers 

Good analytical skills will help you in understanding requirements, breaks down the complex system into smaller units and create corresponding test cases.

As you have to communicate with different teams and sometimes with clients too, so strong communication skills is a must. Not only verbal, but you need a strong written communication skills also as you have to write  test cases, testing plan, bug reports etc.

Nowadays, automation testing is required everywhere and you need technical skills to become handy in automation testing. Technical skills include different automation testing tools like QTP, Loadrunner etc. and also other tools like MS-office, open office, test case writing tools to prepare documents. Knowledge of different type of testing like functional testing, load testing, UI Testing, DB Testing etc. and related testing tools is a must.

Time management is a crucial skill as sometimes, especially when you have to release the code, you need to do everything on time or before time.

To become a successful tester you need passion for it. If software testing doesn't excite you then you can't do in depth testing that is must to make quality software and it affects your growth in career also.