Best Mobile Plus Plan Deals

It's been a while since I've shopped around for a mobile phone and plan bundle, so I'm fishing for some tips.

I'm looking at two main - Optus and Telstra.
Not considering Vodafone because I have poor coverage for some reason.
I'm with Telstra at the moment, but I'm not happy with their support or mandatory Direct Debit.

Is there any places to look for good deals? I remember places sometimes did gift vouchers with sign up, but I don't know where to look for them.

Is there a time of year that is better for deals?

Anything else I'm missing?