What is the correct go-around procedure in a PA-44?
Any procedure listed in the AFM for your airplane takes precedence, but a general go-around technique I use (and teach my own students) is as follows

1) Add power - on complex airplanes, verify mixture rich (or for best power at high altitude airports) and propeller controls are set for maximum RPM prior to pushing the throttles to full power.

2) Apply aft elevator pressure to arrest rate of descent and bring nose level with horizon.

3) With level flight attitude, set flaps from full to approach setting.

4) continue applying aft elevator pressure and establish climb attitude

5) Once climb attitude established and continuous positive rate of climb confirmed, retract the gear.

6) At sufficient airspeed and altitude to permit safely doing so, retract the flaps.

7) Set throttles and propeller controls for maximum continuous power and pitch for selected climb airspeed.  Trim aircraft to neutralize control pressures.