I follow below Test Strategy:
1. First of all i will go through the application.
2. I will prepare the Test Plan (which will includes that how testing will perform, what will be the browsers, OS, Type of testing will perform, Test case preparation, Execution etc.)
3. Based on the functionality i will prepare the Test Cases.
4. Once code ready to Test then i will perform the Smoke Testing to make sure that application is stable for further testing.
5. Once Smoke Test pass then i will execute the Test Cases & will record the testing result Pass/Fail.
6. I will test on various browsers & Operating Systems to make sure its compatible.
7. I will prepare the bug report with the screen shot, if you are using any bug tracking tool then i will post all the issues in to it.
8. I will communicate the bug with development team, so that development team can fix it.
9. Once development team fix it then after i will do regression & Re-testing of application and will close all the bugs.