1) Learn to Analyze your test results thoroughly. Do not ignore any test results. The final test result may be a “pass” or a “fail”, but troubleshooting the root cause of a “fail” will give you the solution to the problem
2) Learn to maximize Test Coverage each time you test any application. 100% test coverage might not be possible but still, you can always try to reach near it.
3) In order to ensure maximum test coverage, break your Application Under Test (AUT) into smaller functional modules. Write test cases on such individual unit modules. Also, if possible break these modules into smaller parts.
4) While Writing Test Cases, you must write test cases for intended functionality first i.e. for valid conditions according to requirements. Then write test cases for invalid conditions. This will cover the expected as well as unexpected behavior of the application under test.
5) If possible identify and group your test cases for Regression Testing. This will ensure quick and effective manual Regression Testing.
6) Applications requiring critical response time should be thoroughly tested for performance. Performance testing is a critical part of many applications.
7) Go beyond Requirement Testing. Test the application for what it is not supposed to do.
8)Note down all such code changes done for testing purposes and at the time of final release make sure you have removed all these changes from the final client-side deployment file resources.
9)Write a clear, descriptive, and unambiguous Bug Report.
10)Practice Stress and load testing.