Hmmm....Oz rules - but not necessarily what the aircraft was originally certified under.
1% climb up to 5000' DH is an Oz requirement - and only applies to *IFR* light twins -hence the somewhat unique Oz IFR weight limit. VFR types only had to be able to maintain altitude.
Elsewhere in the world eg the US FAR 23 under which most (?) were originally certified they only had to have their climb performance 'demonstrated' (<6000 lb MTOW). That can be a negative climb performance. Above 6000 lb TOW then the required climb performance isn't much: along the lines of 0.0027 x the sqr.root Vs (or similar. Can't remember the exact details).
I'm with CC on this with relatively minor variances in technique.
Blue line is the gear up point & that, in turn, is my attempt-to-fly point. I delay gear up if it's a long runway with plenty of room to land on the remaining and get the gear up as soon as I have +ve climb if it's a short/obstacle limiting strip.
I don't have a problem with mixture cuts because I teach (well, taught...) an expectation to land ahead for a failure below blue line & only try to go once gear is selected UP. Gear selected UP is the decision point between landing or trying to fly (but still have a Plan B to force land anyway).
The engine has everything ready to produce maximum power other than adding fuel to the airflow.
As others have mentioned it's prudent to guard the rudder pedals to prevent misapplication. No different to guarding the controls when teaching landings, spin & stall recovery etc.