A: Following are some techniques which can be applied to increase the performance of a JMeter test.
1) Reduce number of concurrent threads :The hardware and server capability limits the number of threads which can run effectively with JMeter.If lot of threads are working simultaneously then each thread has to wait more to get CPU and timing information will be inflated. So it is always better to limit the number of threads.
2) Use proxy server: Use proxy server to filter out all requests which are not important for your testing. Use exclude pattern to filter out unnecessary data.All the files are having their own extensions (like .php, .jsp, .jpeg etc). So use those extensions to set up your exclude pattern.
3) Reduce resource requirements : Following are some measures which can be followed to reduce resources
a) Use non-GUI mode.
b) Use CSV instead of XML output.
c) Use as few listeners as possible.
d) Do not use functional mode.
e) Reduce the number of samplers.
This is a great post
/KP