1/ Make sure the doctor writes it correctly - tablet or capsule strength, total pills ordered AND the words Take as Directed... not Take 1 daily - This is particularly important if you are self-dosing and not strictly following the GP's dosing plan. You could end up with only 90 pills...enough for 1 per day for 90 days.
2/ Make sure whoever faxes your script to PCNZ (you or your pharmacist or dr) - keeps a record of when they sent it so the excuse..."We haven't received the script yet" can be refuted.

I've just been through this farce for the second time... even after dictating word for word what needed to go on the script, my gp (or his receptionist) still got it wrong!
Script went to PCNZ on 28/10 - I finally got  (half) my pills today... 10/11 pretty much 2 weeks all up.