What can be written in private message on www.freelancer.com to get project work?

people are not replying on bid. how to get reply atleast?

I think that on these kind of sites expecting a reply is little naive. Most projects will get so many bids, they won't take the time to reply to them all. I don't have an account, but do they have some kind of skills page? Anything you can put there that will make them interested? Projects you've done, things to show off?

Yes, there is enough space for porfolio and skills and I have added my portfolio on freelancer.com . but I just got 1 reply on 30 bids.

How to impress them in private message and make them to reply?
Private message is the only way to communicate

What would be in a PM to you that would make you consider choosing someone? For me, I'd need verifiable proof of skills.

I am adding my skills and proof of my work, but I'm not receiving reply. So, what can be added more other than skills and proofs?

Well it's really up to the them. Just think about this: when you have like 50 bids on a project it's clear that you will only look at those who have a really nice profile, with lots of similar projects and very good reviews on the site. My advice for you will be to keep on biding, and try to mention similar projects you have done in the message. Try to write up your skills related to that project in the message and also try bidding a little bit lower than others until you get some projects and have some rating.