Lav, you'll need at least 2500 hours - preferably more - and the majority of that should be on commercial jets. Equivalent military experience is fine too. Over and above that, you need to come over well on your CV and covering letter, and it helps if you know someone in the company who can recommend you.
At the moment, the majority of our (relatively few) recruits are ex-low-cost peeps, with 2-3000 hours on 737s.
Scroggs