entry criteria: the set of generic and specific conditions 
for permitting a process to go
forward with a defined task, e.g. test phase. The purpose 
of entry criteria is to prevent a
task from starting which would entail more (wasted) effort 
compared to the effort needed
to remove the failed entry criteria

exit criteria: The set of generic and specific conditions, 
agreed upon with the stakeholders,
for permitting a process to be officially completed. The 
purpose of exit criteria is to
prevent a task from being considered completed when there 
are still outstanding parts of
the task which have not been finished. Exit criteria are 
used to report against and to plan
when to stop testing.

Specifically u have to concentrate on the following points
for the Entry/Exit criteria,Nothing but we have to check all
these before starting our System testing in the SDLC.

Entry Criteria:
1)Whether all the Test scenarios and Test cases prepared or not
2)Whether the software build is ready for testing or not
3)And whether the software/Hardware environment established
to start testing.

Exit Criteria:
1)All the test cases covered or not in the system testing
2)All the open defects fixed or not
3)And whether the software build is working completely or
not as per customer requirements 

So up to my basic knowledge all these are the basic concepts
we have to cover as per the Entry criteria and Exit Criteria
Stages.

Regards
Preethi.G