* we should analyse the bug and mention in which test case 
it belongs

* we should also analyse is this bug belongs to limitation  
and knowni-issue.

*we should put input value expected value and what actual 
value

3 main things that developer would look at which saves his 
time:
Repro-steps
what is the expected result
what is the actual result

Besides
bug identifier
Date
Functional specification number
etc.

1. Bug name
2. Bug Description
3. In which module u r getting
4. What is the severity
5. What is the priority
6. Environments
7. Preconditions
8. Time

One small correction to Uday's answer, never a tester 
decides the priority, it is left to the dev team to decide.

1.Title of the defect
2.Description of the defect
3.Type of defect
4. Severity
5. Attachments of screenshots
6. Steps to reproduce the defect
7. Environment details

If defect is result of failure of test case, always 
associate defect with the test case or else select the 
correct type of the defect if it is general.

Always remember that the tester should specify the defect 
in detail so that developer can understand the problem 
correctly and apply the appropriate solution. Clarification 
time on the defect can be minimized.