assuming that the person whose employment is to be terminated is not the result of IT infractions the above posts are pretty much in line with precautionary practices.
however, if the person is being terminated for IT infractions i assume you have documented the reason(s) or evidence of misdoings.
if you do not have sufficient IT evidence/cause, then you might want to take a step back and do so.
also, if the termination is for IT infractions, then you should take possession of his/her PC, remove the hard drive and document the chain of custody so if it ends up in a law suit you will be best prepared.
the preceeding para should be done the night before you fire the person and he/she should be met at the door first thing in the morning and not allowed to enter the work area. you should have all of their "personal items" in a box for them to take with them.
finally, if you are just now getting around to this "procedure" you should take a look at all of your IT procedures and ensure they are given to all employees, signed and enforced. afterall, you cannot fire someone for something they were never told was against company policy.