Explaining a BUG is an ART for a TESTER...
So...it has lot of things inside
From my learning...I do this!
1. Moment you get the bug, just double check in the bug DB for duplicates. I mean from the earlier build, it might've been uncovered and recorded as a bug and the release manager might've decided to fix it in later builds.
2. Not there in DB, then analyse the bug for confirmation. If you are strongly recomand that as a bug, you can proceed OR please reconfirm with peers
3. Still BUG? So, go ahead use the Bug Tracking database (if any) or use the excel bug reporting format (whatever you have) But, tell everything clear.
a. Bug Title, Bug Description, The setup you have to reproced, the Priority, Impact
b. H/W and S/W used
c. Screen shots, Log file (if any), SQL Qurey statements...If possible record the entire steps in a movie file and send the clip!!!