How to apply for Jobs?

Dear All,

I have cleared CA Final in June 2010 attempt. My industrial training is going to complete on 1st July 2010. The next campus by ICAI will be held in Aug-Sept. 2010. So, I want to start applying for the jobs right now. Please suggest on following:
1) Should i apply only after completion of my training?
2) How to apply in Big companies like PepsiCo, ITC, Wipro, IOC, etc... including big CA Firms?
3) Right now i am recieving job alerts from Naukri.com. Should i also reply to those?

Please Advice.

Regards

Mahesh C. Bansal