An embarrassing confession from me: I've spent a good amount of time in KL on a few separate trips and never once made it up the Petronas Towers

Yes, I know that's bad... What's the secret with the getting tickets for it? I saw a counter in the KLCC basement that supposedly gave away tickets (it's free, right?) but was always closed. Do you have to go early doors? I swear I was there early one morning but it was closed... maybe I was just unlucky with the days.
Does anyone know any other sneaky ways to get tickets without destroying a holiday lie-in or scrumming it with the other tourists in a queue?
Also, can you walk along the connecting bridge of the towers, or is it closed to the public?