Topic: How to do load testing on web application.

I have to test a web application for load.(ie.,) load testing.

For that what i have to do? What are all the tools( free downloadable) to be used?

How to do the load testing like how to fix or decide or how to calculate the hit rate, throughput...etc.

If Astra is a better tool to test the load then how to fix the hit rate, throughput ...etc.

Pl. suggest me to do the load test in a better way.