G'day Anthony , just keep reading and contributing and you'll be a defence junky here in no time!
1. As per the NZ Govt's defence policy framework
http://www.defence.govt.nz/reports-publications/defence-policy-framework/defpol-frmwrk.html#policy see points 19 & 21 etc.
Defence planning (which was your question) occurs at the various political and military levels, even when it comes to NZ equipment purchases. NZ does consult with Australia on its purchases and planning etc, eg in practical terms the ANZAC Frigates, (when we had one) the air combat force, patrol ships, army re-equipping etc. Especially so in the past however what has upset Australia was the incoming NZ Govt in 1999 disbanding the air combat force, reducing the naval combat force in favour of re-prioritising the army, which for Australia (and NZ really) was strategically strange considering both countries are maritime countries, relying on keeping the 'bad guys' at arms length through force projection (Blue water navy, air combat and patrol/surveillence etc), and to keep the sea-lanes open etc.
So NZ's frist line contribution to Australian defence/offence is reduced to a smaller naval combat force, replenishment & maritime patrol.
On the other hand, thanks to 9/11 and regional instability etc, I would suggest the NZ Govt had the biggest fluke it could have possibly not expected, which was for their re-orientation of defence to prioritise the upgrading of the army to perfectly fit the new requirements of Australia, NZ (and other Pacific countries) to help stabilise a number of countries close to home (as well as Afghanistan etc). So the NZ Govt is smarting and (relucantly?) Australia has had to view the changes positively in some respects (i.e. not the non-combat areas but the peace enforcement areas).
2. Yes, well said. The interest groups here that dismiss an invasion of NZ as meaning we ought to downgrade defence capability further, ignore the reality that if Australia is threatened, then ipso facto, so will NZ too either directly or by strangulation.
3. ANZUS = A**US (the NZ link is broken). NZ contributes to Australia (& FPDA) seperate from ANZUS.
4. Don't worry brother, the day Australia is threatened will see NZ assist in its small way. Don't forget we are a smaller nation with a lot less GDP, we just can't afford all the big guns. However IMO we need to do better eg an increase to 2% GDP could potentially see at least one more Frigate, if the political will was there, some sort of ACF even if it were for training the Navy and Army, better ASW/ASuW surveillance (& UAV's) with P-3's armed with stand off missiles, a better mobile SAM system to protect our army and sites of importance, increased army firepower & much more helicopter and transport aircraft (maybe a 3-4 chooks for SAS use and some armed helos for the army). Keep the patrol ships for coast guard and anti-terrorism roles and grow the army numbers. This mostly sounds like the NZDF of the 1960's-90's but with added 21st century capabilities (eg the UAV's, armed P3's and bigger army)! Whether this will happen - under Labour, No, under National, some maybe.