How Much Involved Should a Tester Be in Getting a Bug/Defect Fixed?

"Pleasure in the job puts perfection in the work"

--Aristotle

Usually testers would hunt for defects in the product as per the requirements already defined. They would log a defect for anything that deviates from the requirement specifications. Most testers feel that logging a defect ends his responsibility towards that defect. This should not be the case.
We all know that every team member has his/her responsibility clearly defined:

• QA team finds and verifies the defect.
• Dev team codes and fixes the defect.
• Product Manager(PM) gauges the defect and may choose to get it deferred or fixed(Occasionally).

But that does not mean that a tester should just report a defect and wash hands of the defect. It is very possible that the PM or the Dev member might overlook the defect coz' of various reasons like - title not obvious, vague description, low severity, etc.... A good QA member should take responsibility of each and every bug before a final decision has been done on that bug. It will show that he/she does care about the product and his interest towards his work.

If the tester, with all his knowledge, believes that its a bug, he should try to get it fixed. He should try to convince the developer that "this needs to be fixed". First thing he can do is put down the consequences/impact of the defect within the description. Here "impact" does not imply severity or priority of a defect, rather it is the consequences of not fixing the defect. An example defect would be - "The GUI text field takes >2000 chars, whereas the database table can only store 2000 chars".
That was one simple example, there could be more other varied scenarios depending upon the product. Measuring or judging the impact might come with experience and interest on the product, and a broader view of the product is always profitable to a tester. So a tester can put down his observations first when he logs the defect and next he can talk personally to the developer if required. Well if the developer is still not convinced, we can involve the team leads and then finally the PM can assess the defect on a need basis.

Of-course the tester should take responsibility of the defect till it is fixed, but that does not mean that he should -fight- for each and every defect he logs. He should have some understanding of the product to evaluate which defect should be fixed and which could be deferred. Also, remember that you win some, you lose some, and no product is bug free. He should not escalate each and every defect to the team leads or PM, else his reputation might get a beating :(
Ardent tester often times get into argument with developers upon minor issues, which should be best avoided. More or less the developers will have a slight upper-hand as they do the coding or the fixing part. And don't forget as a tester you are finding fault in their work; who under this sun would like somebody else finding fault in their baby, so always try to be POLITE!!!
Finally, its always effective to have the observations, arguments, or consequences noted down in the defect for everyone to see and come upon a decision on the defect.

Cheers! Have fun making the developer fix your defects!!