Tips on finding bugs

1)Understand the whole application or module in depth before starting the testing.
2)Prepare good test cases before starting off with testing, as in give stress on the functional test cases which includes major risk of the application.
3)Create a sufficient test data before tests, this data set includes the test case conditions and also the database records if you are going to test DB related application.
4)Perform repeated tests with different test environment.
5)Try to find out the result pattern and then compare your results with those patterns.
6)When you think that you have completed most of the test conditions and when you think you are tired somewhat then do some monkey testing.
7)Use your previous test data pattern to analyze the current set of tests.
8)Try some standard test cases for which you found the bugs in some different application. Like if you are testing input text box try inserting some html tags as the inputs and see the output on display page.
9)Last and the best trick is try very hard to find the bug As if you are testing only to break the application!