Some of the best practices for Test Estimation are:
- Add some buffer time: Having a buffer time is always an advantage, it may help to deal with a delay caused due to unexpected reason like talented member quits the job suddenly.
- Account resource planning in estimation: Make sure that your estimation is realistic and considered crucial factors like availability of human resource.
- Use the past experience reference: Through your past experience try to avoid all the obstacles or possible hindrance that are most likely to happen.
- Stick to your estimation: Estimation is not full proof. It may go wrong also. In the early phase of the project, you should re-check the test estimation and if required make modifications as well.