Hi Susheel777:
I have some experience in the management of a technical support group. I think it is important to have an SLA, or Service Level Agreement, which will quantify the support duties. You set target turn around times on sets and subsets of activities, and measure success againt this.
Of course, you need buy-in from the user community and the technical support area when setting acceptable turnaround times, as well as some sort of method of tracking.
A less 'measureable' method is to periodically poll the user community for feedback in the form of on-line survey's etc.
What i find is that your rarely get unsolicited favourable feedback, however, when you go after the information, you will be surprised at the number of users who are satisfied. It is also true that no news is good news, and if you have problem tech support staff, your users will generally let you know.
In terms of actual metrics....that depends on what support duties you handle. If you handle alot of hardware repair, your metrics will be detailed in this area. If you do more software trouble shooting, you will need to breakdown the severity of the problems etc...in order to come up with meaningfull SLA catagories.
You also need to tie in the responsibility of the user in the process as well. For instance, if you are waiting on the user to provide critical information to proceed with the support, you need a way to track this so that it does not reflect poorly on your support staff.
Hope this helps a bit...