It is not the right Idea of doing Load testing Manually.
There are many free tools avalible for load testing like Jmeter.
Supratim If ur application is designed for 1000 user then r u going to use 1000 user seat on computer and run the Scenario? <font color="brown"> </font>
Conducting load testing manually is difficult job and I found to be not of much use. Below factors driven me to depend on automation tools for load testing,
1) No think time between any two successive requests to the application
2) To keep the requests of all users in sync
3) To measure the average respone time
4) To create the load for longer duration
5) To load the system with numerally high concurrency
6) Test repeatability
7) Repeatable simulation of same scenario with same conditions etc.